Mental Math
Find mentally:
4.5 + 2.3 = ?
6.8
Round each number to the nearest whole number:
4.6 + 2.3
Then estimate the sum.
5+2=7
If a base-ten model has:
What decimal does the model represent?
3.42
In 6.482, what is the value of the digit 8?
8 hundredths
Mia has $5.25. Her mom gives her $2.50 more.
How much money does Mia have?
$7.75
Find mentally:
7.6 − 2.4 = ?
5.2
Estimate:
8.72 − 3.18
Round each number to the nearest whole number.
9 − 3 = 6
What decimal is represented by:
5 ones + 7 tenths + 6 hundredths?
5.76
Which number is greater?
4.56 or 4.506
4.56
A runner jogs 3.75 miles on Monday and 2.4 miles on Tuesday.
How many miles did the runner jog altogether?
6.15 miles
Use compensation to solve mentally:
9.8 + 3.7
13.5
Think of 9.8 as 10 and 3.7 as 3.5.
Estimate:
12.48 + 5.61
Round each number to the nearest whole number.
12+6=18
2.4 + 1.35
3.75
Write 7 tenths and 25 hundredths as a decimal.
0.95
A bottle contains 8.5 liters of water. A student drinks 2.75 liters.
How much water remains?
5.75 liters
Solve mentally:
12.5 − 4.9
7.6
Which is the better estimate for:
19.72 − 8.91
A. 5
B. 10
C. 15
D. 20
B. 10
6.2 − 1.45
What number is missing?
3.75 + ___ = 5.00
1.25
A school buys three items:
What is the total cost?
$10.50
Find mentally:
6.75 + 2.25 + 1.50
A student says:
7.82 + 4.19 ≈ 20
Is the estimate reasonable? Explain why or why not.
No. A reasonable estimate is about 12 because 7.82 ≈ 8 and 4.19 ≈ 4, and 8 + 4 = 12.
3.50 − 1.75=?
How many wholes, tenths, and hundredths would you have after solving??
1.75
1 whole
7 tenths
5 hundredths
Put these numbers in order from least to greatest:
2.5, 2.05, 2.55, 2.15
2.05, 2.15, 2.5, 2.55
Jordan has $20.00. He buys a book for $7.85 and a game for $6.75.
How much money does Jordan have left?
$7.85 + $6.75 = $14.60
$20.00 − $14.60 = $5.40