A boat can travel 104 km downstream in 8 hours. If the speed of the stream is 2 km/h, then find in what time will it be able to cover 13 km upstream?
Answer & explanation
Correct answer: option 2
We know that,
Downstream speed = Speed in still water + Speed of stream
Distance = Speed × Time
We have,
The boat can travel 104 km downstream in 8 hours.
Speed of stream = 2 km/h
= Let the speed of the boat in still water be a and the speed on the stream be b.
= 104/(a + b) = 8
= a + b = 13
= a = 2 (given)
= a = 13 – b = 13 – 2 = 11
= Upstream speed = 11 – 2 = 9 km/h
= Distance = Speed × Time
= 13 = 9 × Time
= Time = 13/9 = $1\frac{4}{9}$ hours