Question

A man travels $1^{st}$ 50 km at 25 km/hr next 40 km with 20 km/hr and then 90 km at 15 km/hr Then find his average speed for the whole journey (in km/hr)

Answer 1

Given,

Distance = 50 km, Speed = 25 km/h

Distance = 40 km, Speed = 20 km/h

Distance = 90 km, Speed = 15 km/h

Now, For finding the average speed we must have to find the total time taken

So,

For 1st

$Time=\frac{Distance}{Speed}=\frac{50}{25}=2h$

For 2nd

$Time=\frac{Distance}{Speed}=\frac{40}{20}=2h$

For 3rd

$Time=\frac{Distance}{Speed}=\frac{90}{15}=6h$

Now,

$Averagespeed=\frac{Totaldistance}{Totaltime}=\frac{50+40+90}{2+2+6}=\frac{180}{10}=18km$ /h

Hence the average speed is 18 km/h