Assess Reasonableness of Decimal Sums and Differences

Estimate the sum.

69.9 + 22.1 =

Which difference is about 10?

• 33.2 – 28.4

• 70.9 – 58.7

• 42.5 – 16.8

• 65.7 – 65.6

Estimate the difference.

98 - 5.7 =

Estimate the sum.

9 + 1.2 =

Lina buys a hamburger for $2.96 and a milkshake for $4.06. She pays with a $20 bill. What is a reasonable estimate for how much change she should get back?

Rob hikes 2.89 miles every day for one week straight. At the end of the week, about how many miles did he hike in total?

Which is the best estimate of 61.4 + 88.3?

• 100

• 140

• 150

• 200

Estimate the following sum by first rounding each decimal to the nearest hundred.

428.1 + 186.5 + 210.62

Estimate the sum.

78.5 + 51.2

Estimate the difference.

968.8 - 161