Question

8 + 9 is a near doubles fact. Write the doubles fact 8 + 9 is close to. Then solve. Write another near-doubles addition fact and solve it.

A. 8 + 9 is close to 8 + 8. Solve.
B. 8 + 9 is close to 9 + 9. Solve.
C. 8 + 9 is close to 8 + 10. Solve.
D. 8 + 9 is close to 7 + 9. Solve.

Answer 1

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