Which one of the following uses estimation to check 267-154=113? a. 300-200=100. b. 113+154=267. c. 300-150=150. d. 270-150=120

A. 300-200=100
You round 267 to 300, 154 to 200, and 113 to 100.

A, C and D are all using estimation to check the result. 

A is rounding to the nearest multiple of 100. 
267 --> 300 
154 --> 200 

C is rounding to the nearest multiple of 50. 
267 --> 300 
154 --> 150 

D is rounding to the nearest multiple of 10. 
267 --> 270 
154 --> 150 

Those each give you an estimation of the final answer to see if 113 is a reasonable answer. 

Method B is just switching the values around to check the subtraction using addition. That's a valid way to double check the result, but is NOT estimation. 

If you are only expected to give *one* answer, then method D is the best way to check using estimation because it does the least amount of rounding. 

 
D. 270 - 150 = 120

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