SME
Grade 2 Math · Number & Base Ten
Add and subtract within 1,000
Use this for “What is 245 + 138?” and “What is 383 − 138?”
Picture
Flats are hundreds, rods are tens, small cubes are ones.
This is an example. Type the numbers from your problem to start.
First number
+
Second number
=
Total
Number sentences
245 + 138 = 383
383 − 138 = 245
Good to know
•
Add hundreds to hundreds, tens to tens and ones to ones.
•
Trade 10 ones for a ten, and 10 tens for a hundred, when needed.
•
Subtraction undoes addition: 245 + 138 = 383, so 383 − 138 = 245.
Step-by-step
WE KNOW
First number: 245
Second number: 138
FIND
total
Step 1 · Find total
245 + 138 = ?
Add hundreds, tens and ones. Trade 10 ones for a ten, or 10 tens for a hundred.
1
2
4
5
+
1
3
8
3
8
3
Ones: 5 + 8 = 13
Tens: 40 + 30 = 70
Hundreds: 200 + 100 = 300
Total: 383
Check
Put the numbers back in. Both sides should match.
245 + 138 = 383 ✓
383 − 138 = 245 ✓
Topic check
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