The speed of a boat downstream is 150% more than its speed upstream. If the time taken by the boat for going 80 km downstream and 50 km upstream is 8.2 hours, then what is the speed (in km/h) of the boat downstream?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 25.
Distance/Speed = Time
Let the speed upstream = 100x
So,
Speed of the boat downstream = 100x × 250/100 = 250x
As per the question;
80/250x + 50/100x = 8.2 hours
⇒ 8/25x + 1/2x = 82/10
⇒ (16 + 25)/50x = 41/5
⇒ 41/50x = 41/5
⇒ 1/10x = 1
⇒ x = 1/10
The downstream speed of the boat = 250x
⇒ 250x = 250 × 1/10
⇒ 25 km/h