Question

A truck covers 30km at a uniform speed of 30km/h .What should be it's for the next 90km if the average speed for the entire journey is 60km/h.

Answer 1

★ Question

A car covers 30km at a uniform speed of 30km/h . What should be its speed for the next 90 km if the average speed for the entire journey is 60km/h?

$\rule{230}2$

★ Solution

Given: total distance= 120 km

★ Avg. Speed = 60 km/h

★ Time taken by car to cover 30 km= 30/30= 1 hr

★ Let the speed of car for next 90km be x

So,

★ the time taken to complete 90 km = 90/x

Now,

★ Avg. Speed = total distance/ total time taken

→ 60 = 120/(1+(90/x))

→ 60(x+90)= 120x

→ 60x + 5400 = 120x

→ 60x = 5400

→ x = 90 km/h (speed for next 90 km)

Answer 2

Answer:

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.

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

$30 + x = 120$

There by,

$x = 120 - 30 = 90$

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