SBI PO 20 June 2015 Paper

Speed of boat in still water= x kmph
Speed of current = y kmph.
∴ Rate downstream
= (x + y) kmph.
Rate upstream = (x – y) kmph.
∴

y

x+y

=

1

7

⇒ 7y = x + y
⇒ x = 6y
Again

2.75

x−y

=

11

60

⇒ 11(x – y) = 2.75 × 60 = 165
⇒ x - y =

165

11

= 15
⇒ 6y – y = 15
⇒ 5y = 15
⇒ y = 3 kmph.
∴ x = 6 × 3 = 18 kmph
∴ x + y = Rate downstream
= 18 + 3 = 21 kmph
Distance between points A and
B = Rate downstream × Time
=

21×52

60

= 18.2 km