Subtracting multiples of 10
Subtract multiples of 10 (10–90) from multiples of 10 using place value strategies
What a learner can do afterwards
- Calculate 70 − 30 = 40
- Use base-ten blocks to show 80 − 50 = 30
- Explain that subtracting tens is like subtracting the tens digits
The lesson
A multiple of 10 is made of whole groups of ten. When you subtract two multiples of 10, you are really taking away some of those groups. You already know how to subtract small numbers, so use that same skill on the tens.
Ben has 60 marbles. He gives 20 marbles to his friend. Think: 6 tens take away 2 tens is 4 tens, so 60 minus 20 is 40.
Look at just the tens digits. For 70 minus 30, think 7 minus 3 equals 4. Then put the zero back: the answer is 40, not 4.
To subtract tens, subtract the tens digits, then put the zero back on.
Watch it
Where it sits
This opens up
Nothing builds on it yet.
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
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.