Assessing the Reasonableness of Subtraction Using Rounding

The video tutorial explains how to assess the reasonableness of subtraction problems by using rounding. It introduces the concept of rounding to the leftmost place of the smallest number to check if a subtraction result is reasonable. Two examples are provided: Dana's problem, where the answer is reasonable, and Larry's problem, where the answer is not. The tutorial concludes by reinforcing the importance of using rounding to verify the reasonableness of answers.

What is one method to check if a subtraction answer is reasonable?

• Compare the answer to a similar problem.

• Recalculate the problem using a calculator.

• Ask a friend for their opinion.

• Use rounding to estimate the answer.

In Dana's problem, to which place value are the numbers rounded?

• Thousands

• Hundreds

• Units

• Tens

Why was Dana's answer considered reasonable?

• It was a little higher than the estimated answer.

• It was very close to the estimated answer.

• It was a little lower than the estimated answer.

• It was exactly the same as the estimated answer.

In Larry's problem, to which place value are the numbers rounded?

• Hundreds

• Units

• Thousands

• Ten thousands

Why was Larry's answer not considered reasonable?

• It was too close to the original number.

• It was a little lower than the estimated answer.

• It was off by more than the subtrahend.

• It was exactly the same as the estimated answer.