Common Core: 2nd Grade Math : Operations & Algebraic Thinking

Study concepts, example questions & explanations for Common Core: 2nd Grade Math

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Example Questions

Example Question #431 : Mentally Add And Subtract Within 20: Ccss.Math.Content.2.Oa.B.2

Possible Answers:

Correct answer:

Explanation:

To subtract we can count backwards. Start at  and count back .

Example Question #432 : Mentally Add And Subtract Within 20: Ccss.Math.Content.2.Oa.B.2

Possible Answers:

Correct answer:

Explanation:

To add we count up. Start at  and count up .

Example Question #1 : Determine Even Or Odd Number Of Objects: Ccss.Math.Content.2.Oa.C.3

Is there an even or an odd number of dots below? 

Screen shot 2015 12 01 at 10.43.18 am

 

 

Possible Answers:

Neither

Both

Even

Odd

Correct answer:

Odd

Explanation:

When trying to decide if we have an even or an odd number of items, we can put the items in pairs of two. If each item is in a pair, then we have an even number of items. If there is one item that isn't in a pair, then we have an odd number of items. 

In this case, we have one dot not in a pair, so we have an odd number of dots. 

Example Question #2 : Determine Even Or Odd Number Of Objects: Ccss.Math.Content.2.Oa.C.3

Is there an even or an odd number of dots below? 

Screen shot 2015 12 01 at 10.43.03 am

Possible Answers:

Neither

Even

Odd

Both

Correct answer:

Even

Explanation:

When trying to decide if we have an even or an odd number of items, we can put the items in pairs of two. If each item is in a pair, then we have an even number of items. If there is one item that isn't in a pair, then we have an odd number of items. 

In this case, our dots are in a pair of two, so we have an even number of dots. 

Example Question #3 : Determine Even Or Odd Number Of Objects: Ccss.Math.Content.2.Oa.C.3

Is there an even or an odd number of dots below? 

Screen shot 2015 12 01 at 10.42.14 am

Possible Answers:

Odd

Both

Neither 

Even

Correct answer:

Odd

Explanation:

When trying to decide if we have an even or an odd number of items, we can put the items in pairs of two. If each item is in a pair, then we have an even number of items. If there is one item that isn't in a pair, then we have an odd number of items. 

In this case, we have one dot. This dot is not in a pair, so we have an odd number of dots. 

Example Question #4 : Determine Even Or Odd Number Of Objects: Ccss.Math.Content.2.Oa.C.3

Is there an even or an odd number of dots below? 

Screen shot 2015 12 01 at 10.44.22 am

Possible Answers:

Neither

Even

Odd

Both

Correct answer:

Odd

Explanation:

When trying to decide if we have an even or an odd number of items, we can put the items in pairs of two. If each item is in a pair, then we have an even number of items. If there is one item that isn't in a pair, then we have an odd number of items. 

In this case, we have one dot not in a pair, so we have an odd number of dots. 

Example Question #5 : Determine Even Or Odd Number Of Objects: Ccss.Math.Content.2.Oa.C.3

Is there an even or an odd number of dots below? 

Screen shot 2015 12 01 at 10.44.34 am

 

Possible Answers:

Both

Odd

Neither

Even

Correct answer:

Even

Explanation:

When trying to decide if we have an even or an odd number of items, we can put the items in pairs of two. If each item is in a pair, then we have an even number of items. If there is one item that isn't in a pair, then we have an odd number of items. 

In this case, our dots are in pairs of two, so we have an even number of dots. 

Example Question #6 : Determine Even Or Odd Number Of Objects: Ccss.Math.Content.2.Oa.C.3

Is there an even or an odd number of dots below? 

Screen shot 2015 12 01 at 10.44.45 am

Possible Answers:

Odd

Even

Both

Neither

Correct answer:

Odd

Explanation:

When trying to decide if we have an even or an odd number of items, we can put the items in pairs of two. If each item is in a pair, then we have an even number of items. If there is one item that isn't in a pair, then we have an odd number of items. 

In this case, we have one dot not in a pair, so we have an odd number of dots. 

Example Question #7 : Determine Even Or Odd Number Of Objects: Ccss.Math.Content.2.Oa.C.3

Is there an even or an odd number of dots below? 

Screen shot 2015 12 04 at 9.01.16 am

Possible Answers:

Even

Both

Odd

Neither

Correct answer:

Even

Explanation:

When trying to decide if we have an even or an odd number of items, we can put the items in pairs of two. If each item is in a pair, then we have an even number of items. If there is one item that isn't in a pair, then we have an odd number of items. 

In this case, our dots are in pairs of two, so we have an even number of dots. 

Example Question #8 : Determine Even Or Odd Number Of Objects: Ccss.Math.Content.2.Oa.C.3

Is there an even or an odd number of dots below? 

Screen shot 2015 12 04 at 9.02.12 am

 

Possible Answers:

Both

Even

Neither

Odd

Correct answer:

Odd

Explanation:

When trying to decide if we have an even or an odd number of items, we can put the items in pairs of two. If each item is in a pair, then we have an even number of items. If there is one item that isn't in a pair, then we have an odd number of items. 

In this case, we have one dot not in a pair, so we have an odd number of dots. 

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