Final answer:
Near-doubles addition facts can be solved using related doubles facts. For example, 8 + 9 can be solved by knowing that 8 + 9 is close to 8 + 8. By applying this principle, we can solve all the given near-doubles addition facts.
Step-by-step explanation:
A. 8 + 9 is close to 8 + 8. Solve:
Using the doubles fact 8 + 8, we can solve the near-doubles addition fact 8 + 9 as follows:
8 + 9 = 8 + 8 + 1
= 16 + 1
= 17
B. 8 + 9 is close to 9 + 9. Solve:
Using the doubles fact 9 + 9, we can solve the near-doubles addition fact 8 + 9 as follows:
8 + 9 = 9 + 9 - 1
= 18 - 1
= 17
C. 8 + 9 is close to 8 + 10. Solve:
Using the doubles fact 8 + 10, we can solve the near-doubles addition fact 8 + 9 as follows:
8 + 9 = 8 + 10 - 1
= 18 - 1
= 17
D. 8 + 9 is close to 7 + 9. Solve:
If we use the doubles fact 7 + 9, the solution would be:
8 + 9 = 7 + 9 + 1
= 16 + 1
= 17