Estimating Sums and Differences

Front

What is estimating in math?

Back

Estimating is making a close guess about a number or amount without calculating the exact answer.

Front

How do you estimate a sum?

Back

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

Front

What is the estimated sum of 44 and 62?

Back

100 (44 rounds to 40 and 62 rounds to 60, so 40 + 60 = 100).

Front

What is the estimated sum of 62 and 35?

Back

100 (62 rounds to 60 and 35 rounds to 40, so 60 + 40 = 100).

Front

What is the estimated sum of 43 and 22?

Back

60 (43 rounds to 40 and 22 rounds to 20, so 40 + 20 = 60).

Front

What is the estimated sum of 32 and 49?

Back

80 (32 rounds to 30 and 49 rounds to 50, so 30 + 50 = 80).

Front

How do you estimate a difference?

Back

To estimate a difference, round each number to the nearest ten or hundred and then subtract the rounded numbers.

Front

What is the estimated difference of 50 - 20?

Back

30 (50 rounds to 50 and 20 rounds to 20, so 50 - 20 = 30).

Front

What is the estimated total of 13 and 28?

Back

40 (13 rounds to 10 and 28 rounds to 30, so 10 + 30 = 40).

Front

Why is estimating useful?

Back

Estimating helps us quickly understand the size of a number or how much we have without needing to calculate exactly.