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 =

91 (87 + 4 = 91)

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 hundredths 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
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