Answer:
This is a greatest common factor problem.
What is the greatest common factor of 18 and 30?
18 is 1 x 18: 2 x 9; 3 x 6
30 is 1 x 30: 2 x 15: 3 x 10; 5 x 6
Our greatest common factor is 6.
How many 6 inch boards can you cut from 18 and 30 inches.
18/6 = 3
30/6 = 5
Or, when you find the GCF, it's multiple is the number of boards at that length that can be cut.
