The Airplane Returns

Algebra Level 2

An airplane can travel 320 km/hr in still air. The wind is blowing at 40 km/hr. The total time for journey against the wind is 135 minutes. What will be the time (in minutes) for the return journey? (ignore the take off and landing times of the airplane.)


The answer is 105.

Mehul Arora by Mehul Arora , 20, India

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2 solutions

Montesa Joy Rebao
Oct 22, 2014

let x = t for the return journey

s(w/ the wind)=320+40=360 kph

s(against the wind)=320-40=280 kph

d = s*t

d1=d2

2.25 hours(280)=x(360)

x=1.75hours=105 min

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s=d/t ; s-speed d-distance t-time
let s-c be the speed of the plane against the wind and s+c be the speed of the plane with the wind; c is the current
d1=d2 and d=st
t1(s-c)=t2(s+c)
t1=135mins.
s=32okph
c=40kph
t2=?
135(320-40)=t2(320+40)
135(280)=t2(360)
37800=t2(360)
t2=37800/360
t2=105



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