Two friends A and B are 30 km apart and they start simultaneously on m

1.	Two friends A and B are 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 stops and waits for B to arrive. After how much time (in minutes) A started riding, does B meet A?(a) 15(b) 20(c) 25(d) 30
Answer» Answer is : (d) 30 Let the speed of B = x km/h and the speed of A = 3x km/h Distance between A and B = 30 km Given, distance between them decrease at 2 km per minutes. ∴ Distance decrease in one hour = 2 x 60 = 120 km ∴ Total distance travelled by A and B in one hour = (x+3x) km = 4x km ∴ Speed = 120/4 = 30 km/h Hence, speed of B = 30 km/h Speed of A = 90 km/h Distance travelled by A and B after 10 min = 2 x 10 = 20 km So, remaining distance = (30 - 20) = 10 km Time taken by B to distance travelled 10 km = (10/30 x 60) = 20 min Total time taken by A = 20+10 = 30 min

Two friends A and B are 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 stops and waits for B to arrive. After how much time (in minutes) A started riding, does B meet A?(a) 15(b) 20(c) 25(d) 30

Answer»

Answer is : (d) 30

Let the speed of B = x km/h and the speed of A = 3x km/h

Distance between A and B = 30 km

Given, distance between them decrease at 2 km per minutes.

∴ Distance decrease in one hour = 2 x 60 = 120 km

∴ Total distance travelled by A and B in one hour = (x+3x) km = 4x km

∴ Speed = 120/4 = 30 km/h

Hence, speed of B = 30 km/h

Speed of A = 90 km/h

Distance travelled by A and B after 10 min = 2 x 10 = 20 km

So, remaining distance = (30 - 20) = 10 km

Time taken by B to distance travelled 10 km = (10/30 x 60) = 20 min

Total time taken by A = 20+10 = 30 min