Estimation of Sum and Difference by Rounding

Tens Rounding

100

17+11=?

20+10=30

200

25+23=?

30+20=50

300

43-15=?

40-20=20

400

321-217=?

320-220=100

500

1,762-1,421=?

1,760-1,420=340

Hundreds Rounding

100

261-123=?

300-100=200

200

449+124=?

400+100=500

300

369-182=?

400-200=200

400

1,253-821=?

1,300-800=500

500

2,399+3,422=?

2,400+3,400=5,800

Thousands Rounding

100

1,123+1,528=?

1,000+2,000=3,000

200

2,356-1,029=?

2,000-1,000=1,000

300

4,801-1,910=?

5,000-2,000=3,000

400

11,329-2,683=?

11,000-3,000=8,000

500

22,632-12,921=?

23,000-13,000=10,000