SME
Grade 1 Math · Problem type
Subtract tens
Use this for “Find the value of 80 − 30.”
Picture
Start 70, take away 30.
End 40.
This is an example. Type the numbers from your problem to start.
Start
−
Taken away
=
Left
Number sentences
70 − 30 = 40
Good to know
•
Both numbers are tens: 10, 20, 30, … 90.
•
Take away tens from tens: 7 tens − 3 tens = 4 tens, so 70 − 30 = 40.
Step-by-step
WE KNOW
Start: 70
Taken away: 30
FIND
left
Step 1 · Find left
70 − 30 = ?
Count back by tens: one jump for each ten you take away.
7 tens − 3 tens = 4 tens
Count back by tens: 60, 50, 40
Left: 40
Check
Put the numbers back in. Both sides should match.
70 − 30 = 40 ✓
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