Question

Amith can row a boat d km upstream and the same distance downstream in 5 hours 15 minutes. Also, he can row the boat 2d km upstream in 7 hours. How long will it take to row the same distance 2d km downstream for Amith ?
A) 4 hrs 10 min
B) 3 hrs 15 min
C) 3 hrs 30 min
D) 4 hrs 1 min

Answer 1

$\bf\huge\color{red}{ANSWER}$

Let the speeds of boat and stream was S and V km/hr respectively.
Then, Actual Speed Downstream = (S + V) km/hr.
Actual Speed upstream = (S - V) km/hr.
Given, 

{d / (S+V)} + {d / (S-V )} =5 hrs 15 minutes = 21/4 hours. -------------- (1)
and 2d / (S+V) = 7 -------------- (2)
Now,

d / (S+V)=7/4 
Or, 2d / (S+V)=7/2

Hence, he takes 7/2hours to row 2d km distance downstream.

Answer 2

Hey mate ^_^

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Answer:
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Let the speed of boat and stream be x and y kmph respectively.

According to question,

$\frac{d}{x + y} + \frac{d}{x - y} = 5h \: 15m ---- (1)$

$\frac{2d}{x - y} = 7 ---- (2)$

From eq. (1) and (2)

$\frac{2d}{x + y} = \frac{7}{2}$

Hence,

Amith will take to row 2d km distance downstream in 7/2 hrs.

$= 3.5 hrs$

$= 3 hrs \:30 min$

Therefore,

Correct option C) 3 hrs 30 min

#Be Brainly❤️