Question

A boat went down the river for a distance of 20 km. it then turned back and returned to it starting point, having travelled a total of 7 hours. on its return trip, at a distance of 12 km from the starting point, it encountered a log, which had passed the starting point at the moment at which the boat had started downstream. the downstream speed of the boat is?

Answer 1

Sorry I didn't know the answer so I hope you don't mind it.

Answer 2

Total speed of boat is 7+3=10 km/hr.

Step-by-step explanation:

The formula used is

$\text{Time}=\frac{\text{Distance}}{\text{Speed}}$

Let x be the speed of the water in still water

Let y be the speed of the stream.

The speed in upstream is x-y

The speed in downstream is x+y

According to question,

A boat went down the river for a distance of 20 km. On its return trip, at a distance of 12 km from the starting point.

i.e. $\frac{12}{y}=\frac{20}{x+y}+\frac{8}{x-y}$ .......(1)

Solving (1) equation we get,

$\frac{x}{y}=\frac{7}{3}$

Speed of boat in still water = 7a

Speed of stream = 3a

According to question,

$\frac{20}{x+y}+\frac{20}{x-y}=7$

$\frac{20}{7a+3a}+\frac{20}{7a-3a}=7$

Solving the equation we get,

a=1

Speed of boat in still water = 7

Speed of stream = 3

Total speed of boat is 7+3=10 km/hr.

#Learn more

A boat went down the river for a distance of 20 km. it then turned back and returned to it starting point, having travelled a total of 7 hours. on its return trip, at a distance of 12 km from the starting point, it encountered a log, which had passed the starting point at the moment at which the boat had started downstream. the downstream speed of the boat is?

https://brainly.in/question/2686933