A train is targeted to run from Delhi to Pune at an average speed of 80 kph but due to repairs of track losses 2 hrs in the first part of the journey. If then accelerates at a rate of 20 kph2 till the speed reaches 100 kph. Its speed is now maintained till the end of the journey. If the train now reaches station in time. Find the distance from when it started accelerating.?
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a
840km
b
740km
c
540km
d
640km
answer is A.
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Detailed Solution
If t is normal running time t=l80t1=x180+2; t2=100−8020=1hr; t3=l−x1−x2100 Here x2=801+1220l2⇒x2=90 km Total time ∴t1+t2+t3 t=t1+t2+t3x180+2+1+l−x1−90100=l80l−x1=840km