The speed of boat in still water on Saturday was 21 km/hr. and that on Sunday was `28(4)/(7)%` less than tha on Saturday. Is the time taken by boat to travel upstream on Saturday is `1(3)/(16)` times than time taken to travel downstrean on Sunday, then find the time taken by the boat to cover a distance of `57.6` km upstream when the speed of stream is same as that of Saturday.

Options

A. 3 hrs.
B. 2 hrs.
C. 4 hrs.
D. `2.5` hrs.

Answer

A

Explanation

Given
Speed of boat in still water on Saturday =21 km/hr
`:. 28(4)/(7)%=(2)/(7)`
`:.` Speed of boat in still water Sunday
`=21-(2)/(7)xx21`
`21-6=15` kmph
Accroding to question,
`(10xx18)/(21-x)=(19)/(16)xx(10xx25)/(15+4)`
`x=1.8`
Required time `=(57.6)/(21.1.8)`
`=(57.6)/(19.2)=3 ` hrs.