Subtracting three digits works exactly like subtracting two. There is one more column.
Step 1: Let's Learn
Read it, or press Listen and follow the words.
An example
486 − 253. Hundreds: 2. Tens: 3. Ones: 3. The answer is 233.
Check every column first
Look at all three columns before starting. Any of them might be short.
Take away each kind of block
For 487 - 253: ones, 7 - 3 = 4. Tens, 80 - 50 = 30. Hundreds, 400 - 200 = 200. Together that is 234. When every top digit is big enough, three-digit subtraction is three easy subtractions side by side.
Scan the columns before starting
Look at each column and ask whether the top digit is at least as big as the bottom one. If all three are, the subtraction is straightforward. If not, you will need to open a larger unit, and it is better to know that before you begin.
Check by adding back
234 + 253 should return 487. It does. With three columns there are more places to slip, so this check earns its keep more than ever. Adding back takes less time than redoing the subtraction and is more likely to catch the error.
Step 2: Try It Yourself
Tap and try it out.
Start with
Taken away
What is left
Hundreds
2
Tens
3
Ones
3
486 − 253 = 233
Take 253 away from 486. The faded blocks are the ones that left.
Step 3: Watch an Example
One step at a time.
Watch Leo Subtract
Leo works out 486 − 253.
- Step 1
He checks each column: 6 beats 3, 8 beats 5, 4 beats 2. All fine.
Step 4: Your Turn
Practice makes it stick.
The Warehouse
Problem 1 of 2
A warehouse had 795 boxes and sent out 342. How many are left?
boxes
The Journey
Problem 2 of 2
A trip is 680 km. 250 km are done. How far is left?
km
Three Columns Down
1 of 3
578 − 234 = ?
2 of 3
869 − 415 = ?
3 of 3
396 − 173 = ?
Step 5: Quick Check
Show what you know.
Question 1 of 2
758 − 326 = ?
Question 2 of 2
How many columns do you check before starting?
What You Learned
- Subtracting three digits uses one more column.
- Check every column before you start.
- Take each kind of block from its own kind.