1. Estimate each difference to the nearest ten. Also, find the actual difference.
a) 92 - 47
b) 72 - 21
2. Estimate each difference to the nearest hundred. Also, find the actual difference.
a) 439 - 302
b) 710 - 592
Answer (2)
Let's solve these estimation and subtraction problems step by step:
Estimate each difference to the nearest tens and find the actual difference.
a) 92 - 47
To estimate to the nearest tens, look at the ones place and adjust to the nearest ten.
92 rounds to 90.
47 rounds to 50.
Estimated difference: 90 − 50 = 40
Actual difference: 92 − 47 = 45
b) 72 - 21
72 rounds to 70.
21 rounds to 20.
Estimated difference: 70 − 20 = 50
Actual difference: 72 − 21 = 51
Estimate each difference to the nearest hundreds and find the actual difference.
a) 439 - 302
To estimate to the nearest hundreds, consider the tens place to round.
439 rounds to 400.
302 rounds to 300.
Estimated difference: 400 − 300 = 100
Actual difference: 439 − 302 = 137
b) 710 - 592
710 rounds to 700.
592 rounds to 600.
Estimated difference: 700 − 600 = 100
Actual difference: 710 − 592 = 118
By rounding the numbers involved in your calculation, you get an estimated difference that is often easier to compute mentally. The actual difference helps confirm the precise result.
To estimate differences, round the numbers to the nearest tens or hundreds. The estimated differences for the problems are: a) 40, 50; b) 100, 100. The actual differences are: a) 45, 51; and b) 137, 118.
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