Estimating Sums and Differences

Front

What is estimation?

Back

Estimation is a way to find a number that is close enough to the right answer, usually with some thought about the numbers involved.

Front

How do you estimate a sum?

Back

To estimate a sum, round each number to the nearest ten or hundred, then add those rounded numbers.

Front

What is the difference between exact and estimated answers?

Back

Exact answers are the precise results of calculations, while estimated answers are close approximations.

Front

Why is estimating useful?

Back

Estimating helps us quickly check if an answer is reasonable and can save time in calculations.

Front

What is rounding?

Back

Rounding is changing a number to a nearby value that is easier to work with, often to the nearest ten or hundred.

Front

Estimate the sum of 47 and 36 by rounding.

Back

Round 47 to 50 and 36 to 40. The estimated sum is 50 + 40 = 90.

Front

Estimate the difference of 82 and 29 by rounding.

Back

Round 82 to 80 and 29 to 30. The estimated difference is 80 - 30 = 50.

Front

What is a benchmark number?

Back

A benchmark number is a number that is easy to work with, like 10, 50, or 100, used for estimation.

Front

How can you check if your estimate is reasonable?

Back

You can check if your estimate is reasonable by comparing it to the exact answer.

Front

What is the estimated sum of 23 and 78?

Back

Round 23 to 20 and 78 to 80. The estimated sum is 20 + 80 = 100.