Trains Boats and Streams Practice Test 1 with solutions

Question : 19 of 40

Marks: +1, -0

A boat takes 90 minutes less to travel 36 miles downstream than to travel the same distance upstream. If the speed of the boat in still water is 10 miles/hr, find the speed of the stream.

4 miles/hr
3 miles/hr
2.5 miles/hr
2 miles/hr

Validate

Solution:

Let speed of the stream be x miles/hr, then

{36}/{10-x} - {36}/{10+x}

{90}/{60}

⇒

{48x}/{100-x^2}

= 1
⇒

x^2

+ 48x - 100 = 0
⇒ (x – 2) (x + 50) = 0
∴ x = 2 miles/hr.

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