Two cars P and Q start at the same time from A and B which are 120 km apart. If the two cars travel in opposite directions, they meet after one hour and if they travel in the same direction from A towards B, then P meets Q after 6 hours. What is the speed of the faster car ?
120 km/hr
Incorrect AnswerData inadequate
Incorrect AnswerExplanation:
Let the speed of the car starting from A and B be 'a' and 'b' respectively.
Take the first case. Both cars travel in opposite directions.
Relative speed = a + b
Total distance travelled = 120 km
Time taken = 1 hour
Distance = speed × time
⇒ 120 = a + b ---------> (1)
Take the second case. Both cars travel in same direction. Since A meet B, A is faster than B :-
Relative speed of the faster car = a − b
Total distance travelled = 120 km
Time taken = 6 hours
⇒120 = 6 (a − b)
⇒ 20 = a − b ----------> (2)
(1) + (2) gives :-
2a = 140
⇒ a = 70
Speed of car starting from A = 70 km/hr
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By: Deepak Dawra