The ratio of the speeds of a boat while going upstream and going downstream is 2 : 3 and the sum of these two speeds is 15 km/h. What is the speed of the stream?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 1.5 km/h.
Let the speed of boat upstream be 2z
Speed of the boat in downstream = 3z
According to the question;
Let the speed of the boat and the speed of stream be x and y.
⇒ x + y = 3z and x - y = 2z
We know,
⇒ x + y + x - y = 5z
⇒ 2x = 5z
Now,
⇒ 2x = 15
⇒ x = 7.5 and
⇒ 5z = 15 or z = 3
Hence,
⇒ x + y = 3z
⇒ 7.5 + y = 9
⇒ y = 1.5
Therefore, the speed of the stream = 1.5 km/h