Fact Families (Addition & Subtraction to 20) — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. Which fact belongs in the same family as 6 + 9 = 15?
A) 15 - 6 = 9
B) 15 - 4 = 11
C) 14 - 9 = 5
D) 9 + 3 = 12
A) 15 - 6 = 9 uses the exact same three numbers (6, 9, 15) as 6 + 9 = 15. A fact family always shares the whole and both parts across four related equations.
2. Which number completes the fact family 7, 8, ___?
A) 16
B) 14
C) 15
D) 13
C) 15 completes the family because 7 + 8 = 15, making 15 the whole. The two parts 7 and 8 must add up to the missing number.
3. Which is NOT in the fact family for 5, 6, 11?
A) 5 + 6 = 11
B) 11 - 5 = 6
C) 6 + 6 = 12
D) 11 - 6 = 5
C) 6 + 6 = 12 is the odd one out because it uses 6 twice and reaches 12, not 11. A fact family for 5, 6, 11 must stick to those three numbers only.
4. If 9 + 8 = 17, which subtraction fact is in the same family?
A) 17 - 7 = 10
B) 17 - 9 = 8
C) 16 - 8 = 8
D) 17 - 6 = 11
B) 17 - 9 = 8 reverses the addition by starting with the whole 17 and taking out the part 9, leaving 8. Every addition fact has a matching subtraction partner in its family.
Part B: Fill in the Blank
Write the correct answer on each line.
1. 4 + 7 = 11
Put 6 from the 7 together with the 4 to make 10, then add the last 1 to get 11. This is the first fact in the 4, 7, 11 family.
2. 7 + 4 = 11
Order does not matter in addition, so 7 + 4 gives the same sum as 4 + 7, which is 11. This is the turn-around fact.
3. 11 - 4 = 7
Subtracting the part 4 from the whole 11 returns the other part, 7. The facts 4 + 7 and 11 - 4 undo each other.
4. 11 - 7 = 4
Start at 7 and count up to 11, making 4 jumps in total. So 11 - 7 = 4, the last equation in the 4, 7, 11 fact family.
5. 8 + 6 = 14
To find the missing part, subtract: 14 - 6 = 8. Using a fact family partner quickly solves missing-addend problems.