Question

Abdul, while driving to school, computes the average speed for his trip to be 20 km/ h. What is the average speed for Abdul’s trip?

Answer 1

Correct Question :

Abdul, while driving to school, computes the average speed for his trip to be 20 km/ h. On his return trip along the same route,there is less traffic and the average speed is 30 km/h. What is the average speed for Abdul's Trip.

Solution :

Let the Distance at the school be x.

i) While driving to school,average speed is 20 km/h. Let the time taken be $\sf\: t_{1}$

★ Speed = Distance/Time

→ 20 = $\sf\dfrac{x}{t_{1}}$ hrs

→ $\sf\: t_{1} = \dfrac{x}{20}$ hrs

ii) While returning, the average speed is 30 km/h. Let the time taken be $\sf\: t_{2}$

★ Speed = Distance/Time

→ 30 = $\sf\dfrac{x}{t_{2}}$ hrs

→ $\sf\: t_{2} = \dfrac{x}{30}$ hrs

• Total Distance Covered = Going + Return

→ x + x = 2x km

• Total Time taken = $\sf\: t_{1} + t_{2}$

→ $\sf\dfrac{x}{20} \: + \: \dfrac{x}{30}$

→ $\sf\dfrac{3x + 2x}{60}$

→ $\sf\cancel\dfrac{5x}{60}$

→ $\sf\dfrac{x}{12}$ hrs

Now,

★ Average Speed = Total distance covered/Total time taken

→ $\sf\dfrac{2x \times\: 12}{x}$

→ $\sf\cancel\dfrac{24x}{x}$

→ 24 km/hr

$\therefore$ Average speed for Abdul's trip is 24 kilometers per hour.

Answer 2

Given that:

• Average speed for driving to School is 20 km/hr.

• Average speed for returning back to the home is 30 km/hr.

To Find:

• Average speed for entire journey.

Formula Used:

• Average speed = total distance/total time

Solution:

Let the distance of home from school be x.

Also, let the time taken from home to school be t1 and school to home be t2.

So, ATQ, we have

t1 = x/20....(1)

t2 = x/30 ....(2)

Total distance covered = 2x...(3)

So, Average speed = (3)/[(1)+(2)]

Average speed = 2x/x(1/20+1/30)

Average speed = 2*60/5 = 24 km/hr

So, average speed for entire journey is 24 km/hr.

Hope this helps