Assessing Reasonableness in Sums

This lesson teaches how to assess the reasonableness of sums by using rounding. It explains the importance of checking if an answer is reasonable and provides examples with Lucinda and Tasha to illustrate the process. The lesson emphasizes rounding to the leftmost place of the smallest number to ensure consistency and accuracy in estimation. By comparing the estimated sum with the actual sum, students can determine if their answers are reasonable.

What is the primary method taught in this lesson to check the reasonableness of sums?

• Using a calculator

• Rounding based on place value

• Estimating by guessing

• Rewriting the problem

In Lucinda's example, what is the leftmost place value used for rounding the number 41?

• Thousands

• Hundreds

• Tens

• Units

What was the estimated sum when rounding Lucinda's numbers to the nearest ten?

• 410

• 420

• 430

• 400

Why was Lucinda's answer considered reasonable?

• It was a round number.

• It was a multiple of ten.

• It was very close to the estimated sum.

• It was exactly the same as the estimate.

In Tasha's example, what is the leftmost place value used for rounding the number 912?

• Units

• Tens

• Thousands

• Hundreds

What was the estimated sum when rounding Tasha's numbers?

• 42,000

• 41,000

• 41,300

• 40,000

Why was Tasha's answer considered unreasonable?

• It was off by a large margin.

• It was exactly the same as the estimate.

• It was very close to the estimated sum.

• It was a round number.

What might have gone wrong in Tasha's calculation?

• She used the wrong numbers.

• She used a calculator.

• She lined up the numbers incorrectly.

• She estimated correctly.

What is the key takeaway from this lesson on assessing sums?

• Always use a calculator.

• Rounding helps determine reasonableness.

• Exact answers are always necessary.

• Estimation is not useful.

What should Tasha do after realizing her answer was unreasonable?

• Ask someone else to solve it.

• Use a different method.

• Ignore the mistake.

• Try the problem again.