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
The lesson
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.
Watch it
Where it sits
This opens up
Nothing builds on it yet.
8 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.