This question tests 2nd grade understanding of skip counting by 5s, 10s, and 100s, including recognizing patterns and continuing sequences (CCSS 2.NBT.A.2: Count within 1000; skip-count by 5s, 10s, and 100s). Skip counting means counting by intervals other than 1. When you skip count by 5s, you add 5 each time (5, 10, 15, 20, 25...). When you skip count by 10s, you add 10 each time (10, 20, 30, 40, 50...). When you skip count by 100s, you add 100 each time (100, 200, 300, 400, 500...). To find the next number in a pattern, identify the interval (how much is being added each time) and add that amount. To count backward, subtract the interval instead of adding it. Look at the difference between consecutive numbers to find the pattern. If 20, 30, 40, the difference is 10 each time, so counting by 10s. If 15, 20, 25, the difference is 5 each time, so counting by 5s. In this problem, the pattern is 5, 10, 15, 20, 25, and the student must identify the rule for the pattern. To find the answer, recognize the difference between numbers is 5 so the pattern counts by 5s. Choice C is correct because the pattern shows numbers increasing by 5 each time (5, 10, 15, 20, 25) which is counting by 5s. This correctly applies the skip counting rule. Choice B represents a specific error: identified the wrong pattern (said by 10s when actually by 5s). This error typically happens when students don't identify the correct interval or confuse by 5s with by 10s. To help students: Practice skip counting aloud with the whole class—everyone counts together by 5s (5, 10, 15, 20...), by 10s (10, 20, 30...), by 100s (100, 200, 300...). Use a number line or hundred chart: mark skip counting by highlighting numbers (on a 100-chart, highlight every 5th or 10th number). Connect to real-world: count nickels by 5s (each nickel = 5¢), dimes by 10s (each dime = 10¢), dollar bills by 100s (each dollar = 100¢). Use manipulatives: group objects in 5s or 10s, count groups. Teach pattern recognition: 'Look at two numbers. What's the difference? That's what we're counting by.' For finding next: 'Last number is 40. Pattern adds 10 each time. 40 + 10 = 50.' For backward: 'Subtracting interval. 70 - 10 = 60.' Practice patterns with blanks: 5, 10, __, 20 (what's missing?). Emphasize patterns: by 5s ends in 5 or 0; by 10s ends in 0 (from decade start); by 100s increases hundreds digit by 1. Watch for: adding wrong interval, counting by 1s instead of skipping, confusing forward and backward, off-by-one errors (skipping counts), changing wrong place value.

This question tests 2nd grade understanding of skip counting by 5s, 10s, and 100s, including recognizing patterns and continuing sequences (CCSS 2.NBT.A.2: Count within 1000; skip-count by 5s, 10s, and 100s). Skip counting means counting by intervals other than 1. When you skip count by 5s, you add 5 each time (5, 10, 15, 20, 25...). When you skip count by 10s, you add 10 each time (10, 20, 30, 40, 50...). When you skip count by 100s, you add 100 each time (100, 200, 300, 400, 500...). To find the next number in a pattern, identify the interval (how much is being added each time) and add that amount. To count backward, subtract the interval instead of adding it. Look at the difference between consecutive numbers to find the pattern. If 20, 30, 40, the difference is 10 each time, so counting by 10s. If 15, 20, 25, the difference is 5 each time, so counting by 5s. In this problem, students must count by 100s starting at 200 and find what comes after 500. To find the answer, identify the interval (100s), list from 200: 200, 300, 400, 500, 600, so after 500 is 600 (500 + 100 = 600). Choice B is correct because the pattern adds 100 each time so after 500 is 600 (500 + 100 = 600). This correctly applies the skip counting rule. Choice D represents a specific error: place value error (changed ones or tens instead of hundreds: 510 instead of 600). This error typically happens when students don't identify the correct interval, add the wrong amount, count by 1s habitually, confuse direction, miscount intervals, or change the wrong place value digit. To help students: Practice skip counting aloud with the whole class—everyone counts together by 5s (5, 10, 15, 20...), by 10s (10, 20, 30...), by 100s (100, 200, 300...). Use a number line or hundred chart: mark skip counting by highlighting numbers (on a 100-chart, highlight every 5th or 10th number). Connect to real-world: count nickels by 5s (each nickel = 5¢), dimes by 10s (each dime = 10¢), dollar bills by 100s (each dollar = 100¢). Use manipulatives: group objects in 5s or 10s, count groups. Teach pattern recognition: 'Look at two numbers. What's the difference? That's what we're counting by.' For finding next: 'Last number is 40. Pattern adds 10 each time. 40 + 10 = 50.' For backward: 'Subtracting interval. 70 - 10 = 60.' Practice patterns with blanks: 5, 10, __, 20 (what's missing?). Emphasize patterns: by 5s ends in 5 or 0; by 10s ends in 0 (from decade start); by 100s increases hundreds digit by 1. Watch for: adding wrong interval, counting by 1s instead of skipping, confusing forward and backward, off-by-one errors (skipping counts), changing wrong place value, not recognizing pattern.

This question tests 2nd grade understanding of skip counting by 5s, 10s, and 100s, including recognizing patterns and continuing sequences (CCSS 2.NBT.A.2: Count within 1000; skip-count by 5s, 10s, and 100s). Skip counting means counting by intervals other than 1; when you skip count by 5s, you add 5 each time (5, 10, 15, 20, 25...), by 10s add 10 each time (10, 20, 30, 40, 50...), by 100s add 100 each time (100, 200, 300, 400, 500...); to find the next number, identify the interval and add it, or subtract for backward counting; look at the difference between consecutive numbers to find the pattern, like 20 to 30 is 10 so by 10s, or 15 to 20 is 5 so by 5s. In this problem, the sequence is counting by 10s starting at 40: 40, 50, 60, __, 80, and the student must find the missing number; to solve, identify the interval of 10 (50 - 40 = 10, 60 - 50 = 10), so add 10 to 60 to get 70, which fits before 80 (70 + 10 = 80). Choice B is correct because the pattern adds 10 each time, so the number after 60 is 60 + 10 = 70, continuing the by-10s count. Choice A represents adding a wrong interval like 5 instead of 10 (60 + 5 = 65), which typically happens when students confuse by-5s and by-10s patterns or don't check the difference correctly. To help students, practice skip counting aloud with the whole class—everyone counts together by 5s (5, 10, 15, 20...), by 10s (10, 20, 30...), by 100s (100, 200, 300...); use a number line or hundred chart to mark skip counting by highlighting every 5th or 10th number. Connect to real-world examples like counting nickels by 5s (each nickel = 5¢), dimes by 10s (each dime = 10¢), dollar bills by 100s (each dollar = 100¢); use manipulatives to group objects in 5s or 10s and count the groups; teach pattern recognition by saying 'Look at two numbers, what's the difference? That's what we're counting by,' and for missing numbers, 'Add the interval to the number before the blank'; emphasize patterns like by 5s ends in 5 or 0, by 10s ends in 0; watch for errors like adding the wrong interval, counting by 1s instead, or off-by-one mistakes.

This question tests 2nd grade understanding of skip counting by 5s, 10s, and 100s, including recognizing patterns and continuing sequences (CCSS 2.NBT.A.2: Count within 1000; skip-count by 5s, 10s, and 100s). Skip counting means counting by intervals other than 1. When you skip count by 5s, you add 5 each time (5, 10, 15, 20, 25...). When you skip count by 10s, you add 10 each time (10, 20, 30, 40, 50...). When you skip count by 100s, you add 100 each time (100, 200, 300, 400, 500...). To find the next number in a pattern, identify the interval (how much is being added each time) and add that amount. To count backward, subtract the interval instead of adding it. Look at the difference between consecutive numbers to find the pattern. If 20, 30, 40, the difference is 10 each time, so counting by 10s. If 15, 20, 25, the difference is 5 each time, so counting by 5s. In this problem, the pattern is 900, 800, __, 600, 500, counting backward by 100s, and the student must find the missing number. To find the answer, identify the interval (100s), subtract 100 from 800 (800 - 100 = 700), which fits before 600 (700 - 100 = 600). Choice B is correct because the pattern subtracts 100 each time so the missing number between 800 and 600 is 800 - 100 = 700. This correctly applies the skip counting rule. Choice A represents a specific error: subtracted the wrong interval (pattern by 100s but subtracted 50, giving 850 instead of 700). This error typically happens when students don't identify the correct interval, subtract the wrong amount, or confuse with other patterns like by 50s. To help students: Practice skip counting aloud with the whole class—everyone counts together by 5s (5, 10, 15, 20...), by 10s (10, 20, 30...), by 100s (100, 200, 300...). Use a number line or hundred chart: mark skip counting by highlighting numbers (on a 100-chart, highlight every 5th or 10th number). Connect to real-world: count nickels by 5s (each nickel = 5¢), dimes by 10s (each dime = 10¢), dollar bills by 100s (each dollar = 100¢). Use manipulatives: group objects in 5s or 10s, count groups. Teach pattern recognition: 'Look at two numbers. What's the difference? That's what we're counting by.' For finding next: 'Last number is 40. Pattern adds 10 each time. 40 + 10 = 50.' For backward: 'Subtracting interval. 70 - 10 = 60.' Practice patterns with blanks: 5, 10, __, 20 (what's missing?). Emphasize patterns: by 5s ends in 5 or 0; by 10s ends in 0 (from decade start); by 100s increases hundreds digit by 1. Watch for: adding wrong interval, counting by 1s instead of skipping, confusing forward and backward, off-by-one errors (skipping counts), changing wrong place value.

This question tests 2nd grade understanding of skip counting by 5s, 10s, and 100s, including recognizing patterns and continuing sequences (CCSS 2.NBT.A.2: Count within 1000; skip-count by 5s, 10s, and 100s). Skip counting means counting by intervals other than 1. When you skip count by 5s, you add 5 each time (5, 10, 15, 20, 25...). When you skip count by 10s, you add 10 each time (10, 20, 30, 40, 50...). When you skip count by 100s, you add 100 each time (100, 200, 300, 400, 500...). To find the next number in a pattern, identify the interval (how much is being added each time) and add that amount. To count backward, subtract the interval instead of adding it. Look at the difference between consecutive numbers to find the pattern. If 20, 30, 40, the difference is 10 each time, so counting by 10s. If 15, 20, 25, the difference is 5 each time, so counting by 5s. In this problem, the pattern is 120, 130, 140, 150, __, counting forward by 10s, and the student must find the next number. To find the answer, identify the interval (10s), add 10 to the last number (150 + 10 = 160). Choice B is correct because the pattern adds 10 each time so the next number after 150 is 150 + 10 = 160. This correctly applies the skip counting rule. Choice A represents a specific error: counted by 1s instead of skip counting (gave 151 instead of 160). This error typically happens when students count by 1s habitually, change the wrong place value digit, or don't identify the correct interval. To help students: Practice skip counting aloud with the whole class—everyone counts together by 5s (5, 10, 15, 20...), by 10s (10, 20, 30...), by 100s (100, 200, 300...). Use a number line or hundred chart: mark skip counting by highlighting numbers (on a 100-chart, highlight every 5th or 10th number). Connect to real-world: count nickels by 5s (each nickel = 5¢), dimes by 10s (each dime = 10¢), dollar bills by 100s (each dollar = 100¢). Use manipulatives: group objects in 5s or 10s, count groups. Teach pattern recognition: 'Look at two numbers. What's the difference? That's what we're counting by.' For finding next: 'Last number is 40. Pattern adds 10 each time. 40 + 10 = 50.' For backward: 'Subtracting interval. 70 - 10 = 60.' Practice patterns with blanks: 5, 10, __, 20 (what's missing?). Emphasize patterns: by 5s ends in 5 or 0; by 10s ends in 0 (from decade start); by 100s increases hundreds digit by 1. Watch for: adding wrong interval, counting by 1s instead of skipping, confusing forward and backward, off-by-one errors (skipping counts), changing wrong place value.

This question tests 2nd grade understanding of skip counting by 5s, 10s, and 100s, including recognizing patterns and continuing sequences (CCSS 2.NBT.A.2: Count within 1000; skip-count by 5s, 10s, and 100s). Skip counting means counting by intervals other than 1; when you skip count by 5s, you add 5 each time ($5, 10, 15, 20, 25\ldots$), by 10s add 10 each time ($10, 20, 30, 40, 50\ldots$); by 100s add 100 each time ($100, 200, 300, 400, 500\ldots$); to find the next number, identify the interval and add it, or subtract for backward counting; look at the difference between consecutive numbers to find the pattern, like 20 to 30 is 10 so by 10s, or 15 to 20 is 5 so by 5s. In this problem, the pattern is counting backward by 10s: 90, 80, __, 60, 50, and the student must find the missing number; to solve, identify the interval of 10 ($90 - 80 = 10$, but since backward subtract 10), so subtract 10 from 80 to get 70, which fits before 60 ($70 - 10 = 60$). Choice B is correct because the pattern subtracts 10 each time, so the number after 80 is $80 - 10 = 70$, continuing the backward by-10s count. Choice A represents subtracting a wrong interval like 5 instead of 10 ($80 - 5 = 75$), which typically happens when students confuse backward by-5s and by-10s or don't recognize the direction. To help students, practice skip counting aloud with the whole class—everyone counts together by 5s ($5, 10, 15, 20\ldots$), by 10s ($10, 20, 30\ldots$), by 100s ($100, 200, 300\ldots$); use a number line or hundred chart to mark skip counting by highlighting every 5th or 10th number. Connect to real-world examples like counting nickels by 5s (each nickel = 5¢), dimes by 10s (each dime = 10¢), dollar bills by 100s (each dollar = 100¢); use manipulatives to group objects in 5s or 10s and count the groups; teach pattern recognition by saying 'Look at two numbers, what's the difference? That's what we're counting by,' and for backward, 'Subtract the interval'; emphasize patterns like by 5s ends in 5 or 0, by 10s ends in 0; watch for errors like adding instead of subtracting, confusing direction, or wrong interval.

This question tests 2nd grade understanding of skip counting by 5s, 10s, and 100s, including recognizing patterns and continuing sequences (CCSS 2.NBT.A.2: Count within 1000; skip-count by 5s, 10s, and 100s). Skip counting means counting by intervals other than 1. When you skip count by 5s, you add 5 each time (5, 10, 15, 20, 25...). When you skip count by 10s, you add 10 each time (10, 20, 30, 40, 50...). When you skip count by 100s, you add 100 each time (100, 200, 300, 400, 500...). To find the next number in a pattern, identify the interval (how much is being added each time) and add that amount. To count backward, subtract the interval instead of adding it. Look at the difference between consecutive numbers to find the pattern. If 20, 30, 40, the difference is 10 each time, so counting by 10s. If 15, 20, 25, the difference is 5 each time, so counting by 5s. In this problem, students must count backward by 10s from 90 and find what comes before 70. To find the answer, identify the interval (10s), subtract 10 going backward but since it's before 70, add 10 to 70 (70 + 10 = 80) in the forward sense, or list: 90, 80, 70, so before 70 is 80. Choice B is correct because the pattern subtracts 10 each time backward, so before 70 is 80 (70 + 10 = 80). This correctly applies the skip counting rule. Choice C represents a specific error: added the wrong interval (pattern by 10s but subtracted 5, giving 75 instead of 80). This error typically happens when students don't identify the correct interval, add the wrong amount, count by 1s habitually, confuse direction, miscount intervals, or change the wrong place value digit. To help students: Practice skip counting aloud with the whole class—everyone counts together by 5s (5, 10, 15, 20...), by 10s (10, 20, 30...), by 100s (100, 200, 300...). Use a number line or hundred chart: mark skip counting by highlighting numbers (on a 100-chart, highlight every 5th or 10th number). Connect to real-world: count nickels by 5s (each nickel = 5¢), dimes by 10s (each dime = 10¢), dollar bills by 100s (each dollar = 100¢). Use manipulatives: group objects in 5s or 10s, count groups. Teach pattern recognition: 'Look at two numbers. What's the difference? That's what we're counting by.' For finding next: 'Last number is 40. Pattern adds 10 each time. 40 + 10 = 50.' For backward: 'Subtracting interval. 70 - 10 = 60.' Practice patterns with blanks: 5, 10, __, 20 (what's missing?). Emphasize patterns: by 5s ends in 5 or 0; by 10s ends in 0 (from decade start); by 100s increases hundreds digit by 1. Watch for: adding wrong interval, counting by 1s instead of skipping, confusing forward and backward, off-by-one errors (skipping counts), changing wrong place value, not recognizing pattern.

This question tests 2nd grade understanding of skip counting by 5s, 10s, and 100s, including recognizing patterns and continuing sequences (CCSS 2.NBT.A.2: Count within 1000; skip-count by 5s, 10s, and 100s). Skip counting means counting by intervals other than 1. When you skip count by 5s, you add 5 each time (5, 10, 15, 20, 25...). When you skip count by 10s, you add 10 each time (10, 20, 30, 40, 50...). When you skip count by 100s, you add 100 each time (100, 200, 300, 400, 500...). To find the next number in a pattern, identify the interval (how much is being added each time) and add that amount. To count backward, subtract the interval instead of adding it. Look at the difference between consecutive numbers to find the pattern. If 20, 30, 40, the difference is 10 each time, so counting by 10s. If 15, 20, 25, the difference is 5 each time, so counting by 5s. In this problem, the pattern is 40, 50, 60, 70 and students must continue by 10s to find the next two numbers. To find the answer, identify the interval (10s), add 10 to 70 (70 + 10 = 80), then add 10 to 80 (80 + 10 = 90). Choice B is correct because the pattern adds 10 each time so the next two numbers after 70 are 80 and 90 (70 + 10 = 80, 80 + 10 = 90). This correctly applies the skip counting rule. Choice A represents a specific error: added the wrong interval (pattern by 10s but added 5, giving 75 and 80 instead of 80 and 90). This error typically happens when students don't identify the correct interval, add the wrong amount, count by 1s habitually, confuse direction, miscount intervals, or change the wrong place value digit. To help students: Practice skip counting aloud with the whole class—everyone counts together by 5s (5, 10, 15, 20...), by 10s (10, 20, 30...), by 100s (100, 200, 300...). Use a number line or hundred chart: mark skip counting by highlighting numbers (on a 100-chart, highlight every 5th or 10th number). Connect to real-world: count nickels by 5s (each nickel = 5¢), dimes by 10s (each dime = 10¢), dollar bills by 100s (each dollar = 100¢). Use manipulatives: group objects in 5s or 10s, count groups. Teach pattern recognition: 'Look at two numbers. What's the difference? That's what we're counting by.' For finding next: 'Last number is 40. Pattern adds 10 each time. 40 + 10 = 50.' For backward: 'Subtracting interval. 70 - 10 = 60.' Practice patterns with blanks: 5, 10, __, 20 (what's missing?). Emphasize patterns: by 5s ends in 5 or 0; by 10s ends in 0 (from decade start); by 100s increases hundreds digit by 1. Watch for: adding wrong interval, counting by 1s instead of skipping, confusing forward and backward, off-by-one errors (skipping counts), changing wrong place value, not recognizing pattern.

This question tests 2nd grade understanding of skip counting by 5s, 10s, and 100s, including recognizing patterns and continuing sequences (CCSS 2.NBT.A.2: Count within 1000; skip-count by 5s, 10s, and 100s). Skip counting means counting by intervals other than 1; when you skip count by 5s, you add 5 each time (5, 10, 15, 20, 25...), by 10s add 10 each time (10, 20, 30, 40, 50...), by 100s add 100 each time (100, 200, 300, 400, 500...); to find the next number, identify the interval and add it, or subtract for backward counting; look at the difference between consecutive numbers to find the pattern, like 20 to 30 is 10 so by 10s, or 15 to 20 is 5 so by 5s. In this problem, the pattern is counting forward by 5s: 5, 10, 15, 20, __, 30, and the student must find the missing number; to solve, identify the interval of 5 (10 - 5 = 5, 15 - 10 = 5, etc.), so add 5 to 20 to get 25, which fits before 30 (25 + 5 = 30). Choice C is correct because the pattern adds 5 each time, so after 20 is 20 + 5 = 25, matching the sequence. Choice A represents counting by 1s or adding wrong like 1 (20 + 1 = 21), which typically happens when students fall back to counting by 1s habitually instead of skipping. To help students, practice skip counting aloud with the whole class—everyone counts together by 5s (5, 10, 15, 20...), by 10s (10, 20, 30...), by 100s (100, 200, 300...); use a number line or hundred chart to mark skip counting by highlighting every 5th or 10th number. Connect to real-world examples like counting nickels by 5s (each nickel = 5¢), dimes by 10s (each dime = 10¢), dollar bills by 100s (each dollar = 100¢); use manipulatives to group objects in 5s or 10s and count the groups; teach pattern recognition by saying 'Look at two numbers, what's the difference? That's what we're counting by,' and for missing numbers, 'Add the interval to the number before the blank'; emphasize patterns like by 5s ends in 5 or 0; watch for errors like counting by 1s, wrong interval, or off-by-one.

This question tests 2nd grade understanding of skip counting by 5s, 10s, and 100s, including recognizing patterns and continuing sequences (CCSS 2.NBT.A.2: Count within 1000; skip-count by 5s, 10s, and 100s). Skip counting means counting by intervals other than 1; when you skip count by 5s, you add 5 each time (5, 10, 15, 20, 25...), by 10s add 10 each time (10, 20, 30, 40, 50...), by 100s add 100 each time (100, 200, 300, 400, 500...); to find the next number, identify the interval and add it, or subtract for backward counting; look at the difference between consecutive numbers to find the pattern, like 20 to 30 is 10 so by 10s, or 15 to 20 is 5 so by 5s. In this problem, the student must count backward by 5s from 60 and find what comes before 45; to solve, start from 60 subtracting 5 each time (60, 55, 50, 45...), so the number right before 45 is 50. Choice A is correct because counting backward by 5s from 60 gives 60, 55, 50, 45, so before 45 is 50, applying the skip counting rule correctly. Choice B represents going too far backward or subtracting 10 instead (45 - 5 = 40, but misplaced), which typically happens when students confuse intervals or miscount steps. To help students, practice skip counting aloud with the whole class—everyone counts together by 5s (5, 10, 15, 20...), by 10s (10, 20, 30...), by 100s (100, 200, 300...); use a number line or hundred chart to mark skip counting by highlighting every 5th or 10th number. Connect to real-world examples like counting nickels by 5s (each nickel = 5¢), dimes by 10s (each dime = 10¢), dollar bills by 100s (each dollar = 100¢); use manipulatives to group objects in 5s or 10s and count the groups; teach pattern recognition by saying 'Look at two numbers, what's the difference? That's what we're counting by,' and for backward, 'Subtract the interval'; emphasize patterns like by 5s ends in 5 or 0; watch for errors like subtracting wrong amount, confusing forward and backward, or off-by-one errors.