Ten ones make a ten. Ten tens make a hundred. Same rule, one place up.
Step 1: Let's Learn
Read it, or press Listen and follow the words.
An example
260 + 170. Tens: 6 and 7 makes 13 tens. That is more than ten tens.
Bundle them
Ten of those tens become a hundred, leaving 3 tens. The answer is 430.
Sometimes both
A sum can need a new ten and a new hundred. Do the ones first, then the tens.
When the tens column overflows
Add 274 + 153. The tens give 70 + 50 = 120, which is twelve tens. Ten of those bundle into a hundred and move left, leaving two tens behind. The rule is identical to making a new ten — one column further along.
Finishing the sum
Ones: 4 + 3 = 7. Tens: 7 + 5 = 12 tens, so write 2 and carry a hundred. Hundreds: 200 + 100 plus the carried 100 = 400. Answer: 427. Check against the estimate — about 275 + 150 = 425 — and it holds.
Sometimes both columns carry
In 268 + 175 the ones make 13, carrying a ten, and then the tens make 6 + 7 + 1 = 14 tens, carrying a hundred. Two carries in one sum is normal. Deal with one column at a time and it never becomes complicated, only longer.
Step 2: Try It Yourself
Tap and try it out.
First number
and Second number
Altogether
Hundreds
3
Tens
13
Ones
13
268 + 175 = 443
There are 13 loose ones. Ten of them can become one more ten.
Step 3: Watch an Example
One step at a time.
Watch Ana Make a Hundred
Ana adds 268 and 175.
- Step 1
She adds the ones: 8 and 5 makes 13, so ten of them become a ten.
Step 4: Your Turn
Practice makes it stick.
Two Crowds
Problem 1 of 2
260 people came in the morning and 170 in the afternoon. How many in all?
people
Two Journeys
Problem 2 of 2
A train went 185 km, then 236 km. How far in total?
km
Bundle Where Needed
1 of 4
350 + 280 = ?
2 of 4
164 + 172 = ?
3 of 4
247 + 158 = ?
4 of 4
390 + 240 = ?
Step 5: Quick Check
Show what you know.
Question 1 of 2
275 + 168 = ?
Question 2 of 2
Ten tens bundle into what?
What You Learned
- Ten tens bundle into one hundred.
- Do the ones first, then the tens.
- A sum can need two bundles.