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To the Airport (Posted on 2006-06-27) Difficulty: 2 of 5
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?

See The Solution Submitted by Charlie    
Rating: 4.0000 (2 votes)

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Solution Another Approach | Comment 3 of 4 |
(In reply to Solution by Jyqm)

My final result is in conformity with that of Jyqm, and the methodology culminating in the said result is furnished hereunder as follows:

 

Let (Distance of the airport, Rate of drive) = (D, R)

Then, in terms of provisions of the problem under reference:

(i)                  D/(R+5) = D/R 1/5

(ii)                D/(R-5) = D/R +1/4

So, 25*D/(R(R+5)) = 20*D/(R(R-5)) = 1,

giving, (R-5)/(R+5) = 4/5, so that R = 45

Hence, 25*D = 45*50; giving, D = 90.

Consequently, the airport is 90 MILES AWAY and :

 Joe's current speed is 45 miles per hour . 

(Verification:

  Substituting (D,R) = (90,45) :

in (i) 90/ 50 = 1.8= 90/45- .2

in (ii) 90/40 = 2.25 = 90/45 + .25)

 

Edited on June 27, 2006, 12:13 pm

Edited on June 27, 2006, 12:17 pm

Edited on June 27, 2006, 12:18 pm
  Posted by K Sengupta on 2006-06-27 12:07:28

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