Question

A sailor goes 8 km downstream in 40 minutes and returns in 1 hour.Determine the speed of the sailor in still water and the speed of the current?

Answer 1

your answer is in the photo
after seeing photo see this
from (1)
x+y=12
10 + y = 12
y=2km/hr 
therefore speed of the current is 2km/hr.

Answer 2

Answer:

The speed of the sailor in still water is 10 km/hr and the speed of the current is 2 km/hr

Step-by-step explanation:

Let the sailor speed in still water be x km/hr

And, let the current speed of the be y km/hr

∴ Speed of the boat upstream = (x – y) km/hr

∴ Speed of the boat downstream = (x + y) km/hr

We know, $\text{Speed}=\frac{\text {Distance}}{\text {Time}}$

$\begin{array}{l}{(x+y)=\frac{8}{\frac{40}{60}} \frac{k m}{h r}} \\ {(x+y)=\frac{8 \times 60}{40} \frac{k m}{h r}}\end{array}$

$\begin{array}{l}{x+y=12 \quad \rightarrow(i)} \\ {(x-y)=\frac{8}{1} \frac{k m}{h r}} \\ {x-y=8 \quad \rightarrow(i i)}\end{array}$

$(i) \rightarrow x+y=12$

$(ii) \rightarrow x-y= 8$  

On solving equation (i) and equation (ii), we get

$2 x = 20$

$x=\frac{20}{2}$

$x=10$

Substitute x=10 in (i), we get,

$10+y=12$

$y=12-10$

$y=2$

Hence, the sailor speed in still water is 10 km/hr and the current speed is 2 km/hr