Problem Solving

Adam and beth each drove from smallville to crown city by different routes. Adam drove an average speed of 40 mph and completed the trip in 30 minutes. beth route was 5miles longer, and it took her 20 minutes more than adam to complete the trip how many miles per hour was beth 's average speed on this trip?

answer 30

please explain

Total distance covered by Adam = 40 mph * 30 / 60 min = 20 miles

Beth's distance = 20 + 5 = 25 miles
Beth covers this distance in 30 + 20 = 50 minutes

If 50 minutes => 25 miles, then 60 minutes = 25 / 50 * 60 = 30 mph

Hence Beth's average speed was 30 miles per hour

Thank you, but accoding to the distance formula its

rate * time = distance why do you divide by sixty minutes?

also,

total distance / total time = average speed, why did you divide total distance by 60 min and 50 min.



Im even more confused..could someone explain this to me. I dont want to catch this question on the real GMAT with different numbers and not know exactly how to attack this question...

rate * time = distance

In the problem the rate is givem in mph which is miles per hour and time is in minutes. They have to be brought to a common reference: either hours or minutes.

thank you for clearing that up for me.