SSC CGL Tier II 25 Oct 2015 Paper 1

Question : 100 of 100

Marks: +1, -0

A boat moves downstream at the rate of 1 km in

7 1/ 2

minutes and upstream at the rate of 5 km an hour. What is the speed of the boat in the still water?

Solution:

(2) Rate downstream of boat

= ({{1}/{ {15}/{2 × 60}} ) {kmph}

= {2 × 60}/{15}=8 {kmph}

Rate upstream of boat = 5 kmph
∴ Speed of boat in still water =

1/2

(Rate downstream + Rate upstream)
=

1/2(8+5)=13/2\kmph

=6 1/2\kmph

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