哪位天才指点一下儿，prep1-178

178.       18885-!-item-!-187;#058&011972

Adam and Beth each drove from Smallville to Crown
                    City by different routes.  Adam drove an an average speed of 40 miles per hour and completed the trip in 30 minutes.  Beth's route was 5 miles 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?

(A) 24

(B) 30

(C) 48

(D) 54

(E) 75

完全没人问过，难道我太白痴？

我怎么做都是 （40*0.5 +5）*3=75

为啥答案是B呢？？？？

（40*0.5+5）/（50/60）=30

ls老好人的

原来是看漏了more than...

我退回角落里去了.....