Question

3. A car travels from A to B at a speed of 20 kmhr and returns
at a speed of 30 km/hr. The average speed of the car for
the whole journey is
(a) 25 km/hr
(b) 24 km/hr
(c) 50 km/hr
(d) 5 km/hr​

Answer 1

Answer:

Let the distance between A and B be 'x' km.

Speed of the car from A to B (u) = 20 km/hr

$\boxed{\sf{Time\:{(T_{1})}= \frac{x}{20}}}$

Also,

Speed of the car from B to A (v) = 30 km/hr

$\boxed{\sf{Time\:{(T_{2})}= \frac{x}{30}}}$

Thus,

$\boxed{\sf{Total\:time = T_{1} + T_{2}}}$

So:

$\implies$ x/20+ x/30

$\implies$ x/12 hr

Total distance covered = x + x = 2x

Using formula,

$\boxed{\sf{Average\:speed=\frac{Total\:distance}{Total\:time}}}$

So:

$\implies$ 2x/(x/12)

$\implies$ 24 km/hr

Thus,

Average speed of the car is 24 km/hr.

Therefore:

Correct option: (b) 24 km/hr

Answer 2

b. 24 km/hr .....

HOPE IT HELPSSS!!!!!!!!!!!

(sorry as I can't give explanation)