KVPY SA Exam 2011 Question Paper

Question : 64 of 80

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Two friends A and B arc 30 km apart and they start simultaneously on motorcycles to meet each other. The speed of A is 3 times that of B. The distance between them decreases at the rate of 2 km per minute. Ten minutes after they start, A's vehicle breaks down and A slops and waits for B to arrive. After how much time (in minutes) A started riding, docs B meet A?

Validate

Solution:

Speed of B = V km/hr
Speed of A = 3V km/hr
Given 4V = 2 × 60 km/hr
⇒ V = 30 km/hr
Distance covered by then after 10 min = 2 × 10 = 20 km
so remaining distance = (30 – 20) km = 10 km
Time taken by B to cover 10 km =

10/{30\/ 60}

= 20 min.
Total time = 20 +10 = 30min

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