Multiplying by Tens
Multiply one-digit whole numbers by multiples of 10 in the range 10–90 using strategies based on place value and properties of operations
What a learner can do afterwards
- Calculate 7 × 30 = 210 by reasoning 7 × 3 tens = 21 tens = 210
- Explain why multiplying by a multiple of 10 adds a zero to the product
- Use this skill to estimate products of larger numbers
1 · Read
You already know facts like 6 × 4 = 24. Multiplying by a number such as 40 uses that same fact. Think of 40 as 4 tens. So 6 × 40 means 6 groups of 4 tens, which is 24 tens, or 240.
Look at 6 × 80. First multiply the digits: 6 × 8 = 48. Now think in tens: 80 is 8 tens, so 6 × 80 is 48 tens, which is 480.
Always do the small multiplication fact first. Then place one zero at the end for the ten.
Multiply the digits, then add one zero for the ten.
2 · Watch
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Where it sits
15 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.