Concept 4 of 6
Expanded Form & Number Names
Today's big idea
Expanded form pulls a number apart into the value of each room.
342 is 300 + 40 + 2, the same number in three forms.
How it works
👀 What's going on?
One number can be dressed three ways: in digits, in words, and pulled apart.
💡 Here's the trick
Split a number by its rooms. 342 becomes 300 + 40 + 2. That pulled-apart form is expanded form.
247 = 200 + 40 + 7, and in words it is two hundred forty-seven.
✍️ Try it
Write 305 in expanded form. It is 300 + 5 (there are no tens).
⚠️ Watch out
A 0 in a room adds nothing, but it still holds that room open.
Watch me solve one
Quanta solves it
“Watch how I think through one of these — then you try.”
THE PROBLEM
“Write 408 in expanded form.”
- 1
Read each room
4 hundreds, 0 tens, 8 ones.
- 2
Write the value of each
400 + 0 + 8
- 3
Drop the empty room
Zero tens add nothing, so leave it out.
- 4
Answer ✓
400 + 8
Now you try one — same steps, different story 👇
See it in action
⚡ Time to play!
Slide the smaller cards onto the big 600 card. Line them up on the right and watch the digits cover the zeros!
Pack 600 + 0 + 5 into one number
Quick check
✅ VERIFICATION
What is the expanded form of 620?
⚡ Finish the activity above first to answer.
Keep going!
Up next: Comparing & Ordering to 1000
The first room that differs decides which is bigger.