Use the doubles fact for addition.
4 + 5 = _____
Answer:
9
- Here we need to calculate the sum of 4 and 5.
Let us write 5 as 4 + 1 and use the doubles fact for addition.
We get, 4 + 5 = 4 + 4 + 1
= 8 + 1       [Using the doubles fact: 4 + 4 = 8 ]
= 9 - We get, 4 + 5 = 9.