Bob can drive 50 miles in 40 minutes. Sam can drive 90 miles in 105 minutes. If d is the time (in hours) it takes for Bob to drive 120 miles and e (in hours) is the time it takes for Sam to drive 120 miles, what is the |d-e|? Express your answer as a decimal to the nearest hundredth.

Guest Feb 17, 2020

#1**+1 **

Bob can drive 50 miles in 40 minutes. Sam can drive 90 miles in 105 minutes. If d is the time (in hours) it takes for Bob to drive 120 miles and e (in hours) is the time it takes for Sam to drive 120 miles, what is the |d-e|? Express your answer as a decimal to the nearest hundredth.

Bob drives 50 mi /40 min = (5/4)mi /min

So the time it takes him to drive 120 mi = 120 / [5/4] = 120 * 4 / 5= 96 min = 96/60 = 8/5 hrs

Sam drives 90 /105 = 6/7 mi/ min

So....the time it takes him to drive 120 miles = 120 / [6/7 ] = 120 * 7 / 6 = 140 min = 7/3 hrs

So l d - e l = l 8/5 - 7/3 l = l (24 - 35) / 15 l = l -11 / 15 l = 11/ 15 ≈ 0.73

CPhill Feb 17, 2020