Question

A motorcyclist drives from A to B with a uniform speed of 30kmh-¹ and returns back with a speed if 20 kmh-¹. Find its average speed.​

Answer 1

Answer:

Given:

• A motorcyclist drives from A to B with a uniform speed of 30kmh-¹ and returns back with a speed if 20 kmh-¹.

Find:

• Find its average speed.

Calculations:

• Let x be the common variable used in this question and T as time.

Using formula:

☆ ${\sf{\underline{\boxed{\red{\sf{Time \: taken = \dfrac{Distance}{Speed} }}}}}}$

Calculations:

⇒ $\bold{\dfrac{x}{30} + \dfrac{x}{20}}$

⇒ $\bold{\dfrac{5x}{60}}$

☆ ${\sf{\underline{\boxed{\red{\sf{Average \:Speed = \dfrac{Distance}{Time} }}}}}}$

⇒ $\bold{\dfrac{2x}{\dfrac{5x}{60}}}$

⇒ $\bold{\dfrac{2}{5} \times 60}$

⇒ $\bold{0.24 \times 60}$

⇒ ${\sf{\underline{\boxed{\red{\sf{24 \: km/hr}}}}}}$

Therefore, 24 km/hr is the average speed.

Answer 2

Answer:

24 km/hr

Explanation:

Given :

• Speed of motorcyclist from A to B = 30 km/h

• Speed of motorcyclist from B to A = 20 km/h

To find :

• Average speed of the motorcyclist

Average speed = total distance / total time

Let the total distance = 2X

Time taken = distance / speed

Time taken from A to B = X/30 = X/30

Time taken from B to A = X/20 = X/20

Average

$average \: speed \: = \frac{2x}{ \frac{x}{30} + \frac{x}{20} }$

Taking lcm of 30,20 = 60

$average \: speed \: = \frac{2x}{ \frac{2x}{60} + \frac{3x}{60} }$

$average \: speed \: = \frac{2x}{ \frac{5x}{60} }$

Average speed = 2/5×60

Average speed = 24 km/hr

The average spped of the motorcycle is 24 km/hr