Question

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Answer 1

Given:

On the way to school the average speed for the trip is 20 km/hr and on the way back the average speed is 30 km/hr

To find:

Average Speed of whole trip

Calculation:

Let the distance between home and school be s

$avg. \: v = \dfrac{s + s}{ \frac{s}{20} + \frac{s}{30} }$

$= > avg. \: v = \dfrac{2s}{ \frac{s}{20} + \frac{s}{30} }$

$= > avg. \: v = \dfrac{2s}{ \frac{3s + 2s}{60} }$

$= > avg. \: v = \dfrac{2s}{ \frac{5s}{60} }$

$= > avg. \: v = \dfrac{2 \cancel s}{ \frac{5 \cancel s}{60} }$

$= > avg. \: v = \dfrac{2 \times 60}{5}$

$= > avg. \: v = 24 \: km {hr}^{ - 1}$

So final answer is :

Average Speed is 24 km/hr

Answer 2

GiVeN :-

☛ Average speed of the trip from home to school = 20 km/h

☛ Average speed of the trip from school to home(due to less traffic) = 30 km/h

To DeTeRmInE :-

The average speed of Abdul's total journey.

AcKnOwLeDgEmEnT :-

➽ Distance = Speed × Time

➽ Average speed = Total distance covered/Total time taken

SoLuTiOn :-

Let the distance between Abdul's home and his school be x km.

Case - 1 【Trip from home to school】

➻ Distance = x km

➻ Speed = 20 km/h

Time(t₁) = Distance/Time

⇒t₁ = x/20 h

$\rule{150}2$

Case - 2 【Trip from school to home】

➻ Distance = x km

➻ Speed = 30 km/h

Time(t₂) = Distance/Time

⇒t₂ = x/30 h

$\rule{150}2$

Total distance covered = x + x = 2x km

Total time taken = t₁ + t₂ = (x/20) + (x/30) = (3x + 2x)/60 = 5x/60 = x/12 h

Average speed of the total journey = Total distance covered/Total time taken

→Average speed of the total journey = 2x ÷ (x/12)

→Average speed of the total journey = 2x × (12/x)

→Average speed of the total journey = 2 × 12

→Average speed of the total journey = 24 km/h

∴ The average speed of Abdul in his total journey is 24 km/h.