A boat moves at 12 m/s relative to the water.If the boat is in a river where the current is 2 m/s,how long does it take the boat to make a complete round trip of 1,100 m upstream followed by a 1,100-m trip downstream?
A) 220 s
B) 157.1 s
C) 188.6 s
D) 267.1 s
E) 298.6 s

Question

A boat moves at 12 m/s relative to the water.If the boat is in a river where the current is 2 m/s,how long does it take the boat to make a complete round trip of 1,100 m upstream followed by a 1,100-m trip downstream?
A) 220 s
B) 157.1 s
C) 188.6 s
D) 267.1 s
E) ​298.6 s

Quizplus · Accepted Answer

To find the time taken, we need to first find the speed of the boat with respect to the ground. 
Upstream speed = boat speed - current speed = 12 - 2 = 10 m/s 
Downstream speed = boat speed + current speed = 12 + 2 = 14 m/s

Time taken to travel upstream = distance/speed = 1100/10 = 110 seconds 
Time taken to travel downstream = distance/speed = 1100/14 = 78.57 seconds (approx.)

Total time taken = time upstream + time downstream = 110 + 78.57 = 188.57 seconds (approx.)

Therefore, the answer is C.

A Boat Moves at 12 M/s Relative to the Water