Estimating Sums and Differences

Round to the nearest ten

100

23

20

200

57

60

300

476

480

400

923

920

500

178

180

Round to the nearest hundred

100

890

900

200

147

100

300

555

600

400

451

500

500

2,555

2,600

Estimate the sum

100

43+26=

40+30=70 43+26=69

200

90+37=

90+40=130 90+37=127

300

Round to the nearest ten, then estimate the sum: 172+109=

170+110=About 280
172+109=281

400

205+406

200+400=600 205+406= 611

500

769+445=

800+400=1,200 769+445=1,214

Challenge

100

Solve by rounding to the nearest ten 63-37=

60-40=About 20
Actual answer 63-37=26

200

Solve by rounding to the nearest ten 54-22=

50-20= About 30
54-22=32

300

145-56=

150-60=90 145-56=89

400

Solve by rounding to the nearest ten: 283-256=

280-260=About 20
283-256= 27

500

Solve by rounding to the nearest thousand: 1,778+356+488=

1,800+400+500=About 2,700