Ten ones bundle into a ten. Ten tens bundle into a hundred. Nothing new.
Step 1: Let's Learn
Read it, or press Listen and follow the words.
An example
64 + 52. Tens: 6 and 5 makes 11 tens. That is more than ten tens.
Bundle the tens
Ten of those tens make a hundred, leaving 1 ten. The answer is 116.
Nothing new happens past a hundred
Adding 68 + 54 crosses 100, but the rule is unchanged: ten of any unit bundles into one of the next unit up. Ten ones make a ten; ten tens make a hundred. Crossing a hundred just means the bundling happened in the tens column this time.
A worked case: 68 + 54
Ones: 8 + 4 = 12, so write 2 and carry a ten. Tens: 60 + 50 = 110, plus the carried ten makes 120. That is twelve tens, so ten of them bundle into a hundred. The answer is 122 — one hundred, two tens, two ones.
Estimating catches the big errors
68 is about 70 and 54 is about 50, so expect about 120. When your answer lands near your estimate you can trust it. Estimating will not catch a slip of one or two, but it reliably catches the errors that matter most — the ones off by ten or a hundred.
Step 2: Try It Yourself
Tap and try it out.
First number
and Second number
Altogether
Hundreds
1
Tens
1
Ones
6
64 + 52 = 116
6 tens and 5 tens make 11 tens. Ones go with ones.
Step 3: Watch an Example
One step at a time.
Watch Ana Pass 100
Ana adds 64 and 52.
- Step 1
She counts the cubes: 4 and 2 makes 6. No bundle needed there.
Step 4: Your Turn
Practice makes it stick.
The Sponsored Walk
Problem 1 of 2
Leo raised 75 pounds and Ana raised 60. How much did they raise together?
pounds
Two Boxes
Problem 2 of 2
A box holds 84 marbles and another holds 47. How many marbles in all?
marbles
Over the Hundred
1 of 4
70 + 50 = ?
2 of 4
63 + 54 = ?
3 of 4
86 + 25 = ?
4 of 4
92 + 45 = ?
Step 5: Quick Check
Show what you know.
Question 1 of 2
58 + 67 = ?
Question 2 of 2
How many tens bundle into one hundred?
What You Learned
- Ten ones make a ten. Ten tens make a hundred.
- The rule is the same at every place.
- Answers can go past 100.