Question

A boatman can row 96 km downstream in 8 hr. If the speed of the current is 4 km/hr, then find in what time he will be able to cover 8 km upstream ?

A) 1.5 hrs B) 1 hrs C) 2.5 hrs D) 2 hrs

Answer 1

➲ Solution :

As we know, Speed = Distance /time

Hence, speed in downstream = 96/8 = 12km/hr

Given,

Speed of current = 4km/h

Therefore, speed of the boatman is = 12-4

= 8 km/hr

Speed in upstream = 8-4 =4 km/hr

Hence, time taken to cover 8 km upstream

= 8/4 =2 hours

So, the correct option is D) 2 hours.

✧ Thanks for asking ✧

Answer 2

$\large\bf\underline{Given:-}$

• A boatman can row 96 km downstream in 8 hr.
• the speed of the current is 4 km/hr.

$\large\bf\underline {To \: find:-}$

• Time taken to cover 8 km upstream.

$\huge\bf\underline{Solution:-}$

$\underbrace { \bf \: accourding \: to \: question - }$

A boatman can row 96 km downstream in 8 hr.

• Distance = 96km
• Time = 8hr

$\dag \large \bf \: speed = \frac{distance}{time}$

$\rm \dashrightarrow \: speed = \frac{96}{8} \: \\ \\ \rm \dashrightarrow \:speed \: = 12 \: kmph \:$

• ≫ Speed of current = 4km /hr

Speed of boat in still water = 12 - 4 = 8km/hr.

• Speed of upstream = speed of boat - speed of current.

speed of upstream = 8 - 4

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀= 4km/hr.

Now, Time taken to cover 8km upstream = 8/4

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀= 2hours.

Time taken to cover 8km upstream

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀= 2hours.