A, B and C travel from the same place at the rates of 5, 6 and 8 km/hr respectively. If B starts 2 hours after A, how long after B must C start in order that they may overtake A at the same instant?
Answer:
Say, C starts after time "t" of B and they all meet at a distance "y" from start.
Time taken by A = y/5
Distance covered by B = (y/5 - 2) 6 = y
or, 6y/5 -y = 12
or, y/5 = 12
or, y = 60km
Distance covered by C = (y/5 -2 -t) 8 = y
or, (60/5 - 2 - t )8 = 60
or, (10-t) = 60/8
or, t = 10 - 60/8
or, t = 20/8
or t = 2.5 hours
Answer:
Say, C starts after time "t" of B and they all meet at a distance "y" from start.
Time taken by A = y/5
Distance covered by B = (y/5 - 2) 6 = y
or, 6y/5 -y = 12
or, y/5 = 12
or, y = 60km
Distance covered by C = (y/5 -2 -t) 8 = y
or, (60/5 - 2 - t )8 = 60
or, (10-t) = 60/8
or, t = 10 - 60/8
or, t = 20/8
or t = 2.5 hours
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