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
1 · Read
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.
More to read
Intro to place value: FAQ
Place value gives every digit a job based on where it stands. In 53, the 5 means five tens and the 3 means three ones. Tens blocks and ones cubes make this easy to see and touch. Once you read numbers as tens plus ones, adding and subtracting turn into small steps. Adding ten changes only the tens digit.
Adding 1s and 10s guided practice
Adding ones changes the ones digit, while adding tens changes the tens digit. That pattern lets you jump fast: 34 plus 20 is 54, because 3 tens plus 2 tens is 5 tens. Counting by tens feels like climbing a ladder with big steps. Spot which digit moves and the rest stays put. The same idea works backwards for subtracting ones or tens.
1.5: Subtract Whole Numbers (Part 1)
Subtracting whole numbers means finding what is left or how far apart two counts sit. Start with the ones column, and borrow a ten whenever the top digit is too small. Borrowing swaps one ten for ten ones, so the value never changes. Check with addition, because the missing part plus the taken part must rebuild the start.
Explore more
2 · Watch
En anglaisTake it off screen
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.
18 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.