IBPS PO Prelims Model Paper 11

Upstream distance :
Monday =

18

100

×150 = 27 km.
Tuesday =

12

100

×150 = 18 km.
Wednesday ⇒ 39 km.,
Thursday ⇒ 45 km.
Friday ⇒ 21 km.
Similarly, downstream distance :
Monday ⇒

180×15

100

= 27 km.
Tuesday ⇒

180×25

100

= 45 km.
Wednesday ⇒ 18 km.
Thursday ⇒ 36 km.
Friday ⇒ 54 km.
Let speed of still water upstream on Friday = x kmph,
then downstream speed on Thursday = (10 – x) kmph.
∴

21

x−3

=

36

(10−x)+2.5

⇒12x−36=87.5−7x
⇒12x+7x=87.5+36
⇒19x=123.5
⇒x=

123.5

19

= 6.5 kmph.
∴ Required ratio = 3.5 : 6.5 = 7 : 13