Let speed of the boat be B kmph and one way distance be "d" km.

Total distance in the journey is 2d and the respective upstream and downstream time taken are d/(B-10) kmph & d/(B+10) kmph respectively

Given average speed of the journey is 37.5kmph.

=> 2d / [d/(B-10) + d/(B+10)] = 37.5

=> 2 / [1/(B-10) + 1/(B+10)] =37.5

=> (B-10)(B+10)/B = 37.5

Now use the options and plug in values.

If you use option B and set B-10(Upstream speed)=30=>B=40 then,

at B =40 equation (1) is (40-10)(40+10)/40 =37.5

## A Banana Boat travels from Sunniville to Gloomiville upstream and returns back to Sunniville downstream. If the average speed of the total journey is 37.5 km/hr and the speed of the stream is 10 km/hr, what is the upstream speed of the Bana Print

Modified on: Tue, 12 Oct, 2021 at 12:10 PM

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