perplexus.info :: General : To the Airport

To the Airport (Posted on 2006-06-27)

Joe is driving to the airport to pick up his wife. If he drives at his current speed, he'll arrive on time. If he drives 5 miles per hour faster, he'll arrive 12 minutes early. If he were to drive 5 miles per hour slower instead, he'd arrive 15 minutes late.

How far away is the airport?

Submitted by Charlie

Rating: 4.0000 (2 votes)

Solution: (Hide)

d/r = t
d/(r+5) = t - .2
d/(r-5) = t + .25

rt/(r+5) = t - .2
rt/(r-5) = t + .25

rt = rt + 5t - .2r - 1
rt = rt - 5t + .25r - 5/4

5t = r/5 + 1
5t = r/4 - 5/4

r/5 + 1 = r/4 - 5/4
4r + 20 = 5r - 25
r = 45 miles per hour
t = 2 hours
d = 90 miles

From Mensa calendar for May 10, 2006.

Comments: ( You must be logged in to post comments.)

Subject	Author	Date
solution?	james	2006-06-29 02:11:30
Another Approach	K Sengupta	2006-06-27 12:07:28
Mensa	Mindrod	2006-06-27 09:56:08
Solution	Jyqm	2006-06-27 07:05:46

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