The Iceland team, while rowing, covered a distance of 20 km downstream in 2 hours and the same distance upstream in 5 hours. Find the speed of the stream
Show answer & explanation
Correct answer: A
Explanation
the correct answer is option 1 i.e 3 km/h.
Let's assume the speed in still water and the speed of the stream are 'B' and 'C' respectively.
The Iceland team, while rowing, covered a distance of 20 km downstream in 2 hours and the same distance upstream in 5 hours.
So speed x time = distance
⇒ 2(B + C) =20 Eq.(i)
⇒ 5(B - C) =20Eq.(ii)
So Eq.(i) = Eq.(ii)
⇒ 2(B + C) =5(B-C)
⇒ 2B + 2C = 5B - 5C
⇒ 2C + 5C = 5B - 2B
⇒ B/C = 7/3
⇒ 3B = 7C
So let's assume B = 7y and C = 3y
Put the values of 'B' and 'C' in Eq.(i).
⇒ 2(7y + 3y) = 20
⇒ (7y + 3y) = 10
⇒ 10y = 10
y = 1
speed of the stream = 3y
= 3 × 1
= 3 km/h