Answer: 7 + 7 = 14
8 + 8 = 16
Step-by-step explanation: doubles facts are simply additions where a number is added to it self. The strategy sums up two consecutive numbers when they are next to each other to give their result as given by the question above (8 + 7). We simply add the smaller number together then add one (double-plus-one) OR add the larger number together then subtract one (double-minus-one)
All doubles that can be used in solving 8 + 7 are:
A) 8 + 7 = 7 + (7 + 1) = (7 + 7) + 1 = 14 + 1 = 15 [double-plus-one]
B) 8 + 7 = (8 + 8) - 1 = 16 - 1 = 15 [double-minus-one]
The doubles fact makes use of the associative property of addition —changing the grouping of addends does not change the sum.
