First, find all the factors of the two numbers (separately): <span>72: 1, 2, 3, 4, 6, 8, 9, 12, 18, 24, 36, and 72 </span>48: <span>1, 2, 3, 4, 6, 8, 12, 16, 24, 48 The numbers in bold are factors of both 72 and 48. Find the greatest one (out of the numbers in bold). 24 is the GCF.</span>
It takes her (100 mi)/(50 mi/h) = 2 h to get to her destination. She has 1 h 40 min = 100 min for her 100 mi return trip. .. (100 mi)/(100 min) = (60 mi)/(60 min) = 60 mi/h
She must return at the rate of 60 mph to complete the trip in 3 h 40 min.
