Question

Q.25. A man can row 4 km/h in still water. If the river is
running at 2 km/h, it takes 6 hours to row a place and
back. How far is the place
1) 9 km
2) 11 km
3) 10 km
4) 12 km
5) None of these​

Answer 1

Step-by-step explanation:

Let the distance to the place be x km.

Speed downstream =(4+2) km/hr =6 km/hr

Speed upstream =(4−2) km/hr = 2 km/hr

Given,

x/2+x/6= 6

4x/6=6

4x=36

x=9 km

Answer 2

Question:-

• A man can row 5 km/h in still water. If the river is running at 1 km/h, it takes 75 min to row a place and back. How far is the place.

To Find:-

• Find the distance.

Solution:-

• Let the distance to the place be x

$\sf\longrightarrow \: Speed \: downstreams = 4 + 2$

$\sf\longrightarrow \: Speed \: downstreams = 5 \: kmph$

$\sf\longrightarrow \: Speed \: upstreams = 4 - 2$

$\sf\longrightarrow \: Speed \: downstreams = 3 \: kmph$

Given ,

$\sf\longrightarrow \: \dfrac { x } { 6 } + \dfrac { x } { 2 } = \dfrac { 6 } { 1 }$

$\sf\longrightarrow \: \dfrac { 3x + x } { 6 } = \dfrac { 6 } { 1 }$

$\sf\longrightarrow \: 4x = 6 \times 6$

$\sf\longrightarrow \: x = \cancel\dfrac { 6 \times 6 } { 4 }$

$\sf\longrightarrow \: x = 3 \times 3$

$\sf\longrightarrow \: x = 9$

Hence ,

• Distance is 9 km