Question

A swimmer swims in still water at a speed = 5 km/hr. He enters a 200 m wide river, having river flow
speed - 4 km/hr at point A and proceeds to swim at an angle of 127° (sin37° = 0.6) with the river flow
direction. Another point B is located directly across A on the other side. The swimmer lands on the other
bank at a point C, from which he walks the distance CB with a speed = 3 km/hr. The total time in which he
reachrs from A to B is
(1) 5 minutes
(2) 4 minutes
(3) 3 minutes
(4) None​

Answer 1

Answer:

4 Minutes

Explanation:

A swimmer swims in still water at a speed = 5 km/hr.

swim at an angle of 127°

Speed toward width = 5Sin127 = 5 * 0.8 = 4 km/hr

time Taken = 0.2/4  hr  (200m = 0.2 km )

= 3 Mins

Horizontal Speed = 5 Cos127 = 5 * (-0.6) = -3 km/Hr

Net Flow toward river flow = 4 - 3 = 1 km/hr

Distnce covered in 3 Mins =  (3/60) * 1  = 1/20 km = 50

50 m Covered with a speed of 3 km/hr

Time taken = (50/1000)/3  hr

= 1/60 hr

= 1 min

Total Time taken = 3 + 1 = 4 Minutes