Question

A man can row wkm upstream in 20 minutes and can return in another 15 minutes. His average speed for the entire journey is

Answer 1

Correct Question:

• A man can row 2km upstream in 20 minutes and can return in another 15 minutes. His average speed for the entire journey is

AnSwer:

The average speed would be $6\dfrac{6}{7}$km/hr

GiVen:

• Distance travelled by man (upstream) = 2 km

• Total distance = 2 + 2 = 4 km

• Time taken to travel upstream = 20 min = 1/3 hrs

Similarly,

• Time taken to travel downstream = 15 min = 1/4 hrs

★According to the question,

†Total time taken :-

$\sf : \implies \: \: \dfrac{1}{3} + \dfrac{1}{4} \\ \\ \sf : \implies \: \: \dfrac{4 + 3}{12} \\ \\ \sf : \implies \: \: \dfrac{7}{12}$

Now,

$\longmapsto \: \: { \underline{ \boxed{\sf{ \: Speed = \dfrac{distance}{time}}}}} \\ \\ \sf\longmapsto \: \: \dfrac{4}{ \dfrac{7}{12} } \\ \\ \sf\longmapsto \: \: \dfrac{4}{7} \times 12 \\ \\ \sf\longmapsto \: \: \dfrac{48}{7} \\ \\ \sf\longmapsto \: \: 6\dfrac{6}{7} \: km \: per\: hr$

Therefore, average speed for the entire journey is $6\dfrac{6}{7}$km/hr