Question

A boat can travel 10.5 km upstream in 42 minutes. if the speed of the water current is 1⁄6th of the speed of the boat in still water, how much distance (in km) the boat can travel downstream in 48 minutes ?

Answer 1

the boat speed is 12km.

Answer 2

Answer:

The distance the boat can travel downstream is 4.8 km.          

Step-by-step explanation:

Given : A boat can travel 10.5 km upstream in 42 minutes. if the speed of the water current is 1⁄6th of the speed of the boat in still water.

To find : How much distance (in km) the boat can travel downstream in 48 minutes ?

Solution :

A boat can travel 10.5 km upstream in 42 minutes.

Converting min into hour,

1 hour = 60 min

42 minute = $\frac{42}{60}$ hour.

The speed in the upstream is $S=\frac{D}{T}$

$S=\frac{10.5}{\frac{42}{60}}$

$S=\frac{10.5}{42}\times 60$

$S=15km/hr$

Let the speed of the boat in still water is x km/hr.

If the speed of the water current is 1⁄6th of the speed of the boat in still water then,

The speed of the current is $\frac{x}{6}$

According to question,

$x-\frac{x}{6}=15$

$\frac{5x}{6}=15$

$5x=90$

$x=\frac{90}{15}$

$x=6$

The speed of the boat in downstream is 6 km/hr.

The time taken is 48 minute.

In hour, 48 minute = $\frac{48}{60}$ hour.

The distance is $D=S\times T$

$D=6\times \frac{48}{60}$

$D=4.8$

Therefore, The distance the boat can travel downstream is 4.8 km.