Explanation:
This worksheet is about the
commutative property of addition, which means that changing the order of the numbers being added does
not change the sum. In other words:
a + b = b + a
So, for each problem, we just need to find the missing number that makes both sides equal — usually by swapping the two addends.
Let’s go one by one:
① 1 + 8 = □ + 1
Left side: 1 + 8 = 9
So right side must also be 9 → □ + 1 = 9 → □ = 8
✔ Already filled: 8 (correct)
② 2 + □ = 3 + 2
Right side: 3 + 2 = 5
So 2 + □ = 5 → □ = 3
③ 3 + 5 = □ + 3
Left: 3 + 5 = 8
So □ + 3 = 8 → □ = 5
④ 6 + 5 = □ + 6
Left: 6 + 5 = 11
So □ + 6 = 11 → □ = 5
⑤ 13 + 14 = 14 + □
Left: 13 + 14 = 27
So 14 + □ = 27 → □ = 13
⑥ 5 + 2 = □ + 2
Left: 5 + 2 = 7
So □ + 2 = 7 → □ = 5
⑦ 12 + 15 = □ + 12
Left: 12 + 15 = 27
So □ + 12 = 27 → □ = 15
⑧ 3 + 11 = □
Just add: 3 + 11 = 14
→ □ = 14
⑨ 18 + □ = 9 + 18
Right: 9 + 18 = 27
So 18 + □ = 27 → □ = 9
⑩ □ + 7 = 7 + 11
Right: 7 + 11 = 18
So □ + 7 = 18 → □ = 11
⑪ 21 + 10 = □ + 21
Left: 21 + 10 = 31
So □ + 21 = 31 → □ = 10
⑫ 5 + 12 = □ + 5
Left: 5 + 12 = 17
So □ + 5 = 17 → □ = 12
⑬ 6 + 6 = □ + 6
Left: 6 + 6 = 12
So □ + 6 = 12 → □ = 6
⑭ 7 + 2 = 2 + □
Left: 7 + 2 = 9
So 2 + □ = 9 → □ = 7
Now let’s list all answers in order:
② → 3
③ → 5
④ → 5
⑤ → 13
⑥ → 5
⑦ → 15
⑧ → 14
⑨ → 9
⑩ → 11
⑪ → 10
⑫ → 12
⑬ → 6
⑭ → 7
Final Answer:
3, 5, 5, 13, 5, 15, 14, 9, 11, 10, 12, 6, 7
Parent Tip: Review the logic above to help your child master the concept of associative and commutative property of addition worksheet.
