Mental Math
Rounding Whole Numbers and Decimals
Addition of Decimals
Problem Solving
Subtraction of Decimals
100
Use mental math to add 2.1+0.9+1.2
4.2
100

Round to the nearest ten: 17.4

20

100
Find the sum: 3.28+6.09
9.37
100
Nate has a $5 bill and a $10 bill. He spends $2.50 on a smoothie and $2 for a muffin. How much money does he have left?
$10.50
100
Rose needs 22 hamburgers for a party. She has made 12 hamburgers so far. How many more does Rose need to make? Draw a picture to help!
10 more hamburgers
200
Use mental math to subtract 8.6-4.9
3.7
200

Round to the nearest thousand 427,468

427,000

200
Find the sum: $44.00+$91.46
$135.46
200

Mia planted 15.5 roses, 12.75 geraniums, and 6.25 daisies. Her dog digs up 4.2 roses and 2.15 daisies. How many flowers are left?

28.15 flowers

200
Find the difference: 7.21-6.1
1.11
300
Use compensation to subtract 4.25-3.08
1.17
300
Round to the nearest whole number: 643.82
644
300
Juan adds 3.8+4.6 and gets a sum of 84. Is his answer correct? Write how you know.
No he is not correct because 84 is not close to the estimated answer of 4+5. He forgot to add the decimal point, so the sum should be 8.4
300

Elias saved $30.50 in July, $21.75 in August, and $50.20 in September. He spent $18.35 on movies and $26.45 on gas. Estimate about how much money does Elias have left after spending on movies and gas? Then, find the exact amount of money he has left.

Estimated money left: $103 - $44 = $59

Money left: $102.45 - $44.80 = $57.65

300
Find the difference: $4.08-$2.12
$1.96
400
Use compensation to add $3.47+$4.35
$7.82
400
Round to the nearest hundredth: 0.757
0.76
400
What is the sum of 45.09+2.005
47.095
400

A mason needs 22 bricks to make a stoop. So far, he has carried 15 to the site. How many more bricks must he carry? Draw a part-part whole picture and solve.

7 bricks

400
The pyramid measured 143.5 meters high. The other pyramid measures 65.5 meters high. What is the difference in the heights of the two pyramids?
78 meters
500

On 3 different days at her job, Anne earned $27.50, $33.75 and $49.25. She needs to earn $100 to buy a new desk. The cost of the desk includes tax. If she buys the desk, how much money will she have left over?

$10.50

500
The world's largest blanket measures 4.26 meters around. Round 4.26 to the nearest ones place and to the nearest tenths place.
4 4.3
500
A balloon mural of the Chicago skyline measures 17.6m on one side and 26.21m on the other two sides. What is the perimeter of the mural?
87.62m
500

Dayana picked apples for 2 hours. In the first hour, she picked 28.5 apples. At the end of 2 hours, she had 49.8 apples. How many apples did she pick during the second hour?

21.3 apples

500
An average person's leg bone measures 19.88 inches and the lower leg bone measures 16.94 inches. How much longer is the upper leg bone then the lower leg bone?
2.94 inches
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