Question

A boat man moves downstream at 20 kmph and upstream at 8 kmph. Find the speed of the river?​

Answer 1

Answer:

=> Man's speed with the current = 15 km/hr.

=> Speed of the man + Speed of the current = 15 km/hr.

=> Speed of the current = 2.5 km/hr.

=> Hence, Speed of the man = 15 - 2.5 = 12.5 km/hr.

=> Man's speed against the current = Speed of the Man - Speed of the current = 12.5 - 2.5 = 10 km/hr.

Step-by-step explanation:

Keep Smiling...

Answer 2

Given:

A boat man moves downstream at 20 kmph and upstream at 8 kmph. Find the speed of the river?​

Solution:

Assume that,

Speed of boat is denoted by $\[{S_B}\]$, Speed of river is denoted by $\[{S_R}\]$, Upstream speed is $\[{S_U}\]$ and downstream speed is $\[{S_D}\]$

Therefore,

$\[ \Rightarrow {S_D} = {S_B} + {S_R}\]$

$\[ \Rightarrow 20 = {S_B} + {S_R}\]$            -------(1)

And,

$\[ \Rightarrow {S_U} = {S_B} - {S_R}\]$

$\[ \Rightarrow 8 = {S_B} - {S_R}\]$            -------(2)

Subtract equation (2) from (1),

$\[\begin{array}{l} \Rightarrow 12 = 2{S_R}\\ \Rightarrow {S_R} = 6\,{\rm{kmph}}\end{array}\]$

Hence, the speed of the river is 6 kmph.