Susan drove at an average speed of 30 miles per hour for the first 30 miles of a trip and then at an average speed of 60 miles per hour for the remaining 39 miles of the trip. If she made no stops during the trip, what was susan's average speed, in miles per hour, for the entire trip?
a) 35
b) 40
c) 45
d) 50
e) 55
[不恥下問系列]又有GMAT數學題不懂之10
2009-06-22 8:24 am
回答 (2)
2009-06-22 8:37 am
✔ 最佳答案
The answer is b.
"...for the remaining 39 miles..." should be "...for the remaining 30 miles..."
Otherwise, there is no correct option.
Total distance = (30 + 30) miles = 60 miles
Total time taken = [(30/30) + (30/60)] h = 1.5 h
Average speed = 60/1.5 miles/h = 40 miles/h
=
2009-06-22 8:33 am
（30+39）/（30/30 + 39/60）
= 69 / （1+ 0.65）
= 69 / 1.65
= 41.82 mile/hour
= 69 / （1+ 0.65）
= 69 / 1.65
= 41.82 mile/hour
收錄日期: 2021-04-29 18:18:12
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