A boat is rowed down along a river 21km in 3 hours and against a river 14km in 7 hours. Find the speed of the boat and the river.
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 4.5 km/h and 2.5 km/h.
Speed of boat = B
Speed of river = R
Downstream speed = B + R = 21 / 3 = 7
Upstream speed = B - R = 14 / 7 = 2
Downstream speed = 21 / 3 = 7
Upstream speed = 14 / 7 = 2
B + R = 7
B - R = 2
B = 4.5, R = 2.5
The speed of the boat is 4.5 km/h and the speed of the river is 2.5 km/h.