Question

A covered half of his journey at 20 km/h and rest at x km/h, then his average speed is 24 km/h. what is the value of x?

Answer 1

Average speed=24km/h
half of the journey=20km/h
remaining = x km/h

24km/h=distance -1

20km/h+ x km/h=distance -2

from 1&2
24 km/h=20km/h+x km/h
x=24-20

x=4

it help you

Answer 2

Let the Total Distance be d km and Time taken be T

And According to question,

d/2 ×1/t = 20 km / h

And simplifying this we get 

Time taken = d/40                 ............1

Also he covers the other half by speed x

Then,

d/2 × 1/t = x km/h

Simplifying this we get,

Time taken = d/2x               .............2

Adding 1 and 2 

Total time taken ⇒ d/40 + d/2x

                         T ⇒ dx + 20d / 40x
 
                         T ⇒ d(x + 20) / 40x

And so,

Average speed = Total distance / Total time

                    24 = d / d(x + 20) / 40x

                    24 = 40x / (x + 20)

        24(x + 20) = 40x

        24x + 480 = 40x

         40x - 24x = 480

                  16x = 480

                      x = 30 km/hr

Hence x = 30 km/hr

☺ Hope this Helps ☺