SAT Math : Arithmetic

Study concepts, example questions & explanations for SAT Math

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Example Questions

Example Question #1 : Sets

A team has a win-loss ratio of 4:1. If the team wins six games in a row, the win-loss ratio will now be 6:1. How many losses did the team have initially?

Possible Answers:

2

3

4

1

5

Correct answer:

3

Explanation:

If a team's ratio of wins to losses increases from 4:1 to 6:1 by winning six games, they must have 12 wins initially and 3 losses. 

Example Question #1 : How To Find The Missing Number In A Set

Find the missing number in the following set:

Possible Answers:

Correct answer:

Explanation:

The rule is as follows: add 2 to the previous number then multiply times 2.

The answer is (16 + 2) * 2 = 36.

Example Question #6 : Sets

You have the following data set:

.

Find the missing number  in the data set.

Possible Answers:

Correct answer:

Explanation:

In order to find the missing number (X), you must first identify the pattern in the set of numbers. Upon a glance, you can determine that the pattern starts with 4 and then the next number is 2n+1, with n being the preceding number in the set.

For example, let's start with 4. Multiplying 2*4+1 gives us 9, the next number in the set. 

Therefore, the missing number in the set is .

Example Question #2 : How To Find The Missing Number In A Set

Boxes

A sequence of boxes is constructed, the first six of which are seen above. What number is in the lower right corner of the ninth box?

Possible Answers:

Correct answer:

Explanation:

The lower right number of each box is the sum of the other three numbers, which are found as follows:

The upper left numbers are simply the natural numbers in order;

The upper right numbers are the powers of 2, beginning with ;

The lower left numbers are the terms of the Fibonacci sequence, which is formed by setting the first two terms equal to 1 and each subsequent term equal to its predecessors.

Therefore, the ninth box in the sequence includes the number 9 as its upper left entry, and  as its upper right entry. The lower left entry is the ninth Fibonacci number, which can be found as follows:

The lower right entry is the sum of the other entries:

Example Question #1 : How To Find The Number Of Integers Between Two Other Integers

A custom-made ruler is 30\ cm long and for every 2\ cm there's a tick mark. How many tick marks are there on the ruler?

Possible Answers:

16

14

18

15

17

Correct answer:

16

Explanation:

There will be 15 gaps of 2\ cm long but 16 tick marks because there will be a tick mark on each end of the ruler.

Example Question #2 : How To Find The Number Of Integers Between Two Other Integers

Four consecutive odd integers sum to 40. How many of these numbers are prime?

Possible Answers:

Correct answer:

Explanation:

Let x equal the smallest of the four numbers. Therefore:

\dpi{100} x + (x+2)+(x+4)+(x+6)=40

\dpi{100} 4x +12 = 40

\dpi{100} 4x + 28

\dpi{100} x=7

Therefore the four odd numbers are 7, 9, 11, and 13. Since all are prime except 9, three of the numbers are prime.

Example Question #3 : How To Find The Number Of Integers Between Two Other Integers

The positive integer  is not divisible by . The remainder when  is divided by  and the remainder when  is divided by  are both equal to . What is

Possible Answers:

Correct answer:

Explanation:

We know that the remainder, , must be less than  by the definition of remainder. Therefore our only choices are , , or . We can test each of these cases. 

If   would be divisible by , which we said is not true. 

If : Try . Then . When we divide  by , we have a remainder of . This works! 

If : Try . Then . When we divide this by , we have a remainder of . Thus, our remainders are not equal. 

 

Thus,

Example Question #4 : How To Find The Number Of Integers Between Two Other Integers

How many integers lie between  and , including the end points? 

Possible Answers:

Correct answer:

Explanation:

Let's look at a small example, the numbers between 1 and 3 including all endpoints. We have 1, 2, and 3. If we subtract our numbers, we get 2. We need to add one more to get all the desired numbers. We can follow the same process with our larger numbers. 

 

Take,

 .

Then, adding 1,  

.

Therefore, our answer is 

Example Question #3 : How To Find The Number Of Integers Between Two Other Integers

Mrs. Lovell assigns her reading class to read pages three through sixty-four of their textbook. How many pages must each student read? 

Possible Answers:

Correct answer:

Explanation:

To count the number of pages in between these two page numbers, we want to subtract  and then add . We have to add  because if we don't, we end up not counting either the first or last page of the selection. 

Therefore, our answer is 

Example Question #1 : How To Find The Number Of Integers Between Two Other Integers

How many integers are between  and , inclusive? 

Possible Answers:

Correct answer:

Explanation:

An important consideration whenever you're asked for the number of integers between two other numbers is to determine whether the two "end points" are included. Here the word "inclusive" tells us that we need to count both -8 and 17 in our calculation.

A helpful tip for these questions: if you're including both end points, you can calculate by using the range (greatest value minus smallest value) and adding 1 to account for the inclusive set.  (If you need to prove that to yourself, just use "how many integers between 1 and 3 inclusive" - clearly the set is 1, 2, 3 for three integers, but 3-1 = 2, so you can see you need to add one more to get the answer).

For this question, that leaves us with 17 - (8) = 25 as the range, and if you add 1 to that for "inclusive" you get the correct answer, 26.

Another way to look at this one is to chop it up: between -8 and 17 there are 8 negative integers (-1 through -8), 17 positive integers (1 through 17), and 0 as one more integer.  8 + 17 + 1 = 26. 

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