You already know 3 + 1 = 4. Tens work exactly the same way.
Step 1: Let's Learn
Read it, or press Listen and follow the words.
Count the rods
3 tens and 1 ten makes 4 tens. That is 30 + 10 = 40.
Rods go with rods. You are counting tens, not ones.
It is the same fact in bigger clothes
2 tens and 3 tens is 5 tens, because 2 and 3 is 5. You are counting bundles instead of ones.
The unit is what changed
Nothing about the arithmetic is new. Only what you are counting changed, from ones to tens.
Step 2: Try It Yourself
Tap and try it out.
First number
and Second number
Altogether
Tens
4
Ones
0
30 + 10 = 40
3 tens and 1 tens make 4 tens. Ones go with ones.
Step 3: Watch an Example
One step at a time.
Watch Ana Add Tens
Ana works out 20 + 10.
- Step 1
She counts the rods: 2 rods and 1 rod.
Step 4: Your Turn
Practice makes it stick.
Two Boxes
Problem 1 of 1
Leo has 20 crayons. He gets a box of 10 more. How many?
crayons
Add the Tens
1 of 3
10 + 10 = ?
2 of 3
20 + 20 = ?
3 of 3
30 + 10 = ?
Step 5: Quick Check
Show what you know.
Question 1 of 2
20 + 10 = ?
Question 2 of 2
10 + 30 = ?
What You Learned
- A ten is something you can count.
- 3 tens and 1 ten is 4 tens.
- 30 + 10 = 40.