28: 1, 2, 4, 7, 14, 28
40: 1, 2, 4, 5, 8, 10, 20, 40
The common factors are 1, 2, and 4.
You can use a factor rainbow to help you find the factors (:
Joe completes an average of (10 ft)/(5 h) = 2 ft/hour. Bill completes an average of (10 ft)/(4 h) = 2.5 ft/hour. Together, they complete 2+2.5 = 4.5 ft/hour. At that rate, it will take them
... (120 ft)/(4.5 ft/h) = 26 2/3 h
Step 1: plug in the numbers. 7(6)-4
Step 2 multiply 7x6 42-4
