Problems based on Time & Distance

Ques 2. How long will a train 100 m long travelling at speed 72kmph overtake another train which is 200m long travelling at 54kmph?

A)1min.         B)2min        C)10min          D)0.1min

Ans: A
total speed=72-54=18 km/h=18*5/18=5 m/sec
total length=200+100=300 m
time=300/5=60 sec
so train will overtake another train in 1 minute(ans)

Ques 3. Ravi is travelling on his cycle and has calculated to reach point A at 4 P.M. if he travels at 10 kmph, he will reach there at 12 noon if he travels at 15 kmph. At what speed must he travel to reach A at 1 P.M.?

A)     8 kmph    B)     11 kmph
C)     12 kmph    D)     24 kmph

Ans D
    Let the distance travelled by x km.
    than x/15 -x/10 =4
    3x-2x= 120
     x= 120km
    Time taken to travel 120 km at 10 km/hr = (120/10)hrs = 12hrs
    So, Robert started 12 hours before 4 P.M. i.e., at 4 A.M.
    hence, Required speed = (120/5) kmph = 24 kmph

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