A lady reaches her office 20 mins late by travelling at a speed of 20 km/h and reaches 15 mins early by travelling at a speed of 30 km/h. By how much time(early or late) will she reach her office if she travels at 25 km/h?

1 Answer
Binayaka C.
Nov 27, 2016

Travelling at #25# km/hr she will reach #1# mt early.

Explanation:

Let the distance of the office be #x# Km
Time taken at #20# km/hr is #x/20# hr; reaches #20/60=1/3#hr=20mt late
Time taken at #30# km/hr is #x/30# hr; reaches #15/60=1/4#hr=15mt early
Therefore #x/20-x/30=1/3+1/4 or x/60=7/12 or x=7/12*60=35#Km
Time taken at #30# km/hr is #35/30=35/30*60 =70#mt
Time taken at #25# km/hr is #35/25 =7/5 hr=7/5*60=84 mt#;
So travelling at #25# km/hr she will reach #70+15-84 =1#mt early.[Ans]

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