Question

A car covers 30 km at a uniform speed of 30 km/hr. What should be its speed for the next 90 km if the average speed for the entire journey is 60 km/hr ?
( ans is 90 km/hr speed
but when we try answer comes 9 km/hr)

Answer 1

total distance = 30+90=120
if avg. spd is 60 km/h then total time to cover the dist. is 2 hour.
avg spd.= (30+x)/2

distance=spd * time

120=(30+x)/2*2
120=30+x
x=120-30=90
i.e spd = 90 km/h

Answer 2

The speed of the car for next 90 km is 90 km/hr.

Given data:

The speed of car which covers 30 km = 30 km/h

The average speed of the journey = 60 km / hr

To find:

The speed of the car for next 90 km  = ?

Solution:

To find the average speed for the whole journey, we need to find the mean value of the given speed values.

$60=\frac{30+x}{2}$

$30 + x = 120$

Thereby,

$x = 120 - 30 = 90$

Therefore, the speed for the rest of the travel is 90 km/hr.