IBPS RRB Officer Prelims 14 Nov 2016 Shift 3 Paper

(3) Let the speed of currentbe x kmph.
∴ Speed of boat in still water= 6x kmph.
∴ Rate downstream of boat= 6x + x = 7x kmph.
Rate upstream
= 6x – x = 5x kmph.
According to the question,

105

7x

+

105

5x

=12
⇒

15

x

+

21

x

=12
⇒

36

x

=12⇒12x=36
⇒x=

36

12

=3
∴Speed of boat in still water= 6 × 3 = 18 kmph.