Mental Math

Mental Math

Rounding Whole Numbers & Decimals

Estimating Sums & Differences

Adding & Subtracting Decimals

Problem Solving

100

Use mental math to solve:
2.1 + 0.9 + 1.2 =

4.2

100

Round the number to the tenth place:
1.32

1.3

100

Round to the nearest ten to estimate:
49 + 22 =

70 (50 + 20 = 70)

100

Find the sum:
0.82 + 4.21 =

5.03

100

Miami's annual precipitation n 2000 was 61.05 in. Albany's was 46.92 in. How much greater was Miami's precipitation than Albany"s?

14.13 in.

200

Use mental math to solve:
66 + 1.8 + 2.2 =

70

200

Round to the ten thousands place:
427,841

430,000

200

Round to the nearest hundred to estimate:
179 + 277 =

500 (200 + 300= 500)

200

Find the sum:
6.9 + 2.8 =

9.7

200

Reilly adds 45.3 and 3.21. Should his sum be greater than or less than 48? Tell how you know without actually solving the problem.

Greater than 48 because the whole numbers add up to 48.

300

Use mental math to solve:
3.8 + 1.5 =

5.3

300

Round to the nearest whole number:
643.82

644

300

Round to the nearest whole number to estimate:
87.2 + 3.9 =

92 (88 + 4 = 92)

300

Find the Difference:
7.8 - 4.9 =

2.9

300

Nate has a $5 bill and a $10 bill. He spends $2.50 for a smoothie and $2 for a muffin. How much money does he have left?

$10.50

400

8.6 - 4.9 =

3.7

400

Round to the thousandths place:
23.009

23.01

400

Estimate to the whole number:
3.8 + 4.1 + 3.3 =

11 (4 + 4 + 3 = 11)

400

Find the difference:
65.18 - 12.005 =

53.175

400

Elias saved $30 in July, $21 in August, and $50 in September. He spent $18 on movies and $26 on gas. How much money does Elias have left?

$57

500

Use mental math to solve:
3.99 + 3.11 + 6.3 =

13.4

500

Round 95.25 to the nearest WHOLE #, TENTH, and TEN:

Whole #: 95
Tenth: 95.3
Ten: 100

500

Estimate the difference to the nearest whole number:
12.97 - 3.95 =

9 (13 - 4 = 9)

500

Find the difference:
34.49 - 12.619 =

21.871

500

Fill in the blanks to complete the difference:
6. __ __
- __. 3 9
___________
1 . 8 6

6. 2 5
- 4. 3 9
______
1. 8 6