A boat takes 27 minutes to go 37.2 km upstream. The ratio of the speed of the boat in still water to that of the stream is 8 : 5. How much total time (in hours) will the boat take to go 79.4 km upstream and 85.8 km downstream?

Correct option is B

Given:

Time to go 37.2 km upstream = 27 minutes

The ratio of the speed of the boat in still water to that of the stream is 8 : 5

We need to find the total time to go 79.4 km upstream and 85.8 km downstream 

Formula Used: ​

Speed = $$\frac{Distance }{Time}$$

Solution: ​

Let speed of boat is B and speed of stream be S 

So, Speed of boat = 8x 

speed of stream = 5x 

Now,

8x - 5x = $$\frac{37.2\times 60 }{27} = \frac{248}{3}$$ km/h

x = $$\frac{248}{9}$$km/h

Time taken to cover 79.4 km upstream

= $$\frac{79.4 \times 3}{ 248} = 0.96 h$$ 

Time taken to cover 75.8 km downstrream;

= $$\frac{85.8\times 9}{13 \times 248}= 0.239 hr$$ 

Now, total time = 0.96 + 0.23 = 1.19$$\approx 1.2 hr$$​​