SME
Grade 5 Math · Problem type
Multiply a decimal by a decimal
Use this for “What is 0.6 × 0.3?” with tenths times tenths.
Diagram
0.4 = 4 tenths
0.3 = 3 tenths
4 tenths × 3 tenths = 12 hundredths. 0.4 × 0.3 = 0.12.
Columns and rows overlap in the solid squares: each is 1 hundredth.
This is an example. Type your own values to start a new problem.
First decimal
×
Second decimal
=
Product
Formulas
0.4 × 0.3 = 0.12
First decimal × second decimal = product
Assumptions
•
Multiply the digits as whole numbers: 4 × 3 = 12.
•
Tenths times tenths are hundredths, so the product has two decimal places: 0.12.
•
Both numbers are tenths, from 0.1 to 9.9.
Step-by-step
WE KNOW
First decimal: 0.4
Second decimal: 0.3
FIND
product
Step 1 · Find product
0.4 × 0.3 = ?
First decimal × second decimal = product
Multiply the tenths as whole numbers. Tenths times tenths are hundredths: two places.
4 tenths × 3 tenths = 12 hundredths
12 hundredths = 0.12
Product = 0.12
Check
Put the numbers back in. Both sides should match.
0.4 × 0.3 = 0.12 ✓
Topic check
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Related lessons
Add, subtract, multiply and divide decimals
Main lesson
Multiply decimals and whole numbers
Use this for “A notebook costs $1.65. How much do 14 notebooks cost?”
Divide decimals by whole numbers
Use this for 7.2 ÷ 4: a decimal shared into equal parts.
Subtract decimals
Use this for “Subtract: 5.27 − 2.85 = ___.”
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.