ACT Math : How to subtract odd numbers

Study concepts, example questions & explanations for ACT Math

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Example Questions

Example Question #1 : How To Subtract Odd Numbers

Tom has twice as many chores as Jeff, who has 3 less than Steve.  Steve has 10 chores. How many chores does Tom have? 

Possible Answers:

Correct answer:

Explanation:

If Steve has 10 chores, Jeff has 7 chores (3 less than Steve).  Tom has twice as many as Steve, so Tom has 14 chores. 

Example Question #2 : How To Subtract Odd Numbers

Your mom made  cookies. You ate , your brother ate twice as many as you did, and your sister ate . How many are left?

Possible Answers:

Correct answer:

Explanation:

Create an equation for the situation described and solve:

Example Question #3 : How To Subtract Odd Numbers

Your mom gives out  total presents each year to your cousins. If your cousin Sally received  and your cousin Billy received  times as many as Sally, how many did your  cousin, Becky get?

Possible Answers:

Correct answer:

Explanation:

Create an equation to decribe the above situation and solve.

Total presents given out is represented by .

Presents given to Sally is represented by .

Presents given to Billy is represented by .

Thus our equation becomes,

Example Question #4 : How To Subtract Odd Numbers

Possible Answers:

 

 

 

 

 

Correct answer:

 

Explanation:

Always start by gathering your facts. You know that if  is odd, then neither of those numbers are even. (If either were, then the product would be even.)  Now, the rules for subtracting are just like adding. If the difference of two numbers is even, then they must either both be odd or both be even. Thus if  is even and we know that  is odd, then we know that  must be odd. Thus if  is odd, it is also true that  is even, for both  and  are even.

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