SSC CHSL Model Paper 12

Question : 61 of 100

Marks: +1, -0

A motorboat, whose speed is 15 km/hr in still water, goes 30 km downstream and comes back in a total of 4 hours 30 minutes. The speed of the stream (in km/hr) is:

Validate

Solution:

Let the speed of stream be a.
4 hours 30 minutes

=4+30/60=9/2

hour
Now ,

30/{15+a}+30/{15-a}=9/2

⇒

120 × 15 = 9 (15 - a)(15 + a)

⇒

40× 5 = 225 - a^2

⇒

a^2 = 25 ⇒a = 5

Thus, a = 5 km/hr

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