SME
Grade 1 Math · Operations & Algebraic Thinking
Add and subtract within 20
Use this for “8 birds sit on a fence. 5 more come. How many birds now?”
Picture
8 + 5 = 13
● First number ○ Second number
This is an example. Type the numbers from your problem to start.
First number
+
Second number
=
Total
Number sentences
8 + 5 = 13
13 − 5 = 8
Good to know
•
All numbers are 0 to 20.
•
Make a ten: 8 + 5 = 8 + 2 + 3 = 10 + 3.
•
Subtraction undoes addition: if 8 + 5 = 13, then 13 − 5 = 8.
•
Give the total and one part to find the missing part.
Step-by-step
WE KNOW
First number: 8
Second number: 5
FIND
total
Step 1 · Find total
8 + 5 = ?
Make a ten first, then add the rest.
8 + 2 = 10
10 + 3 = 13
Total: 13
Check
Put the numbers back in. Both sides should match.
8 + 5 = 13 ✓
13 − 5 = 8 ✓
Topic check
See what you know: 5 questions on this topic
New questions each time. Pass to mark it complete.