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Mental Math
Estimation
Addition
Subtraction
100

Use mental math to add.

227 + 218 =

445

100

Round to the hundreds place to estimate the sum.

319 + 652 + 331 =

1,300

100

1,111 + 345 + 33 = 

1,489

100

905 - 769 =

136

200

Use mental math to add. 

522 + 231 =


753

200

Round to the thousands place to estimate the sum.

2,019 + 1,752 + 4,831 = 

9,000

200

4,488 + 1,234 =

5,722

200

8,012 - 555 = 

7,457

300

Use mental math to subtract.

379 - 176 =

203

300

Round to the hundreds place to estimate the difference.

5,345 - 1,199 =

4,100

300

5,202 + 4,888 = 

10,090

300

7,205 - 2,088 =

 5,117

400

Use mental math to subtract.

648 - 220 =

428

400

Round to the thousands place to estimate the difference.

15,702 - 7,390 = 

9,000

400

888 + 123 + 222 = 

1,233

400

9,306 - 3,218 =

6,088

500

Make a ten. What is the missing number?

213 + 255 = 210 + ______ = 468

258

500

Round to the thousands place to estimate the difference.

24,689 - 11,492 = 

14,000

500

8,888 + 7,777 + 6,666 = 

23,331

500

8,000 - 2,123 =

5,877