SME
Grade 5 Math · Number & Base Ten
Add, subtract, multiply and divide decimals
Use this for “A pumpkin weighs 12.5 kg and a melon 3.75 kg. What do they weigh together?”
Diagram
12.5 + 3.75 = 16.25
This is an example. Type your own values to start a new problem.
First number
+
Second number
=
Total
Formulas
12.5 + 3.75 = 16.25
First number + second number = total
Assumptions
•
Line up the decimal points, so tenths sit under tenths and hundredths under hundredths.
•
Add or take away each place from the right, regrouping like whole numbers.
•
The point in the answer goes under the other points. Numbers to 999.99.
Step-by-step
WE KNOW
First number: 12.5
Second number: 3.75
FIND
total
Step 1 · Find total
12.5 + 3.75 = ?
First number + second number = total
Line up the points. Add hundredths, then tenths, then ones, regrouping as you go.
1
1
2
.
5
0
+
3
.
7
5
1
6
.
2
5
Total = 16.25 (about 13 + 4 = 17)
Check
Put the numbers back in. Both sides should match.
12.5 + 3.75 = 16.25 ✓
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Divide whole numbers by two-digit divisors
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Multiply decimals and whole numbers
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More problem types
Multiply decimals and whole numbers
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Divide decimals by whole numbers
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Subtract decimals
Use this for “Subtract: 5.27 − 2.85 = ___.”
Multiply a decimal by a decimal
Use this for “What is 0.6 × 0.3?” with tenths times tenths.
Divide by a decimal
Use this for “How many 0.5s are in 3?” (3 ÷ 0.5), or 0.24 ÷ 0.08.
Estimate sums of decimals
Use this for “About how much is 12.65 + 8.3?” by rounding each to the nearest whole number.
Estimate differences of decimals
Use this for “About how much is 12.65 − 8.3?” by rounding each to the nearest whole number.
Estimate products of decimals
Use this for “About how much is 4.8 × 6.2?” by rounding each to the nearest whole number.