You know 3 + 2 = 5. So 3 hundreds and 2 hundreds make 5 hundreds.
Step 1: Let's Learn
Read it, or press Listen and follow the words.
Written out
300 + 200 = 500. Only the flats changed.
And backwards
700 − 400 = 300, because 7 flats take away 4 flats leaves 3.
Whole hundreds behave like single digits
If you know 3 + 4 = 7, then 300 + 400 = 700. You are adding three hundred-blocks to four hundred-blocks and getting seven of them. The unit changed but the count did not, which is why this is easy the moment you notice it.
The same shortcut for subtraction
800 - 500 is 8 - 5 in hundreds, so the answer is 300. This works for tens too: 80 - 50 = 30. Any time both numbers are whole amounts of the same unit, you can work with the counts and put the unit back at the end.
When the numbers are not whole hundreds
The shortcut only applies when both numbers are whole hundreds. For 340 + 200 you can still use it on the hundreds part: 300 + 200 = 500, then put the 40 back to get 540. Splitting off the easy part is a strategy in itself.
Step 2: Try It Yourself
Tap and try it out.
First number
and Second number
Altogether
Hundreds
5
Tens
0
Ones
0
300 + 200 = 500
0 tens and 0 tens make 0 tens. Ones go with ones.
Step 3: Watch an Example
One step at a time.
Watch Ana Add Hundreds
Ana works out 400 + 300.
- Step 1
She counts the flats: 4 and 3.
Step 4: Your Turn
Practice makes it stick.
Two Schools
Problem 1 of 2
One school has 300 pupils and another has 500. How many altogether?
pupils
The Fundraiser
Problem 2 of 2
A target of 900 pounds has 400 raised so far. How much is still needed?
pounds
Whole Hundreds
1 of 4
200 + 600 = ?
2 of 4
500 + 500 = ?
3 of 4
800 − 300 = ?
4 of 4
600 − 600 = ?
Step 5: Quick Check
Show what you know.
Question 1 of 2
400 + 500 = ?
Question 2 of 2
700 − 200 = ?
What You Learned
- A hundred is a unit you can count.
- 3 hundreds and 2 hundreds make 5 hundreds.
- Only the hundreds digit changes.