Question

A motorcyclist drives from A to B with a uniform speed of 30 km h
−1
and returns with a speed of 20 km h
−1
. Find the average speed.

Answer 1

Answer:

• 24 Km/h is the average speed.

Explanation:

Given:

• A motorcyclist drives from A to B with a uniform speed of 30 Km/h and returns with a speed of 20 Km/h.

To find:

• Average speed of the motorcyclist.

Solution:

Let the distance between A and B be D.

Now,

Time taken by the motorcyclist with speed of 30 Km/h :-

⇒ Time = Distance/Speed

• D/30 hr

Time taken by the motorcyclist with speed of 20 Km/h :-

• D/20 hr

Now,

Average speed of the motorcyclist is :-

⇒ Avg. speed = Total distance/Total time

• (D + D )/(D/30 + D/20)
• (2D)/[(D(2) + D(3)/60]
• (2D)/[5D/60]
• (2D)/12D
• 12 × 2
• 24

∴ The average speed of the motorcyclist is 24 Km/h.

Answer 2

Answer:

average speed = total distance / total time

so here

av speed = 2V1V2/ V1+ V2

= 2× 30×20/30+20

=2×600/ 50

= 1200/ 50 = 24

Explanation:

SO average speed = 24m/s