Question

A car travels from A to B at a speed of 20 km/hr and returns at a speed of 30 km Ihr . The average speed of the car for the whole journey is
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Answer 1

Explanation:

Average speed = Total distance/Total time

Distance =Speed × Time

let's say that distance between A to B is x

Time(A-B)= x/20kmph= x/20 hr

Time(B-A)= x/30kmph = x/30 hr

Total Time = (50/600)x hr

Total Distance =2x

Average speed= (2x)/{(50/600) (x)}=1200/50 kmph

=24 kmph

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Answer 2

$\Large\underline{\underline{\sf Given:}}$

• Car travels from A to B with speed 20km/h and returns at speed of 30km/h

$\Large\underline{\underline{\sf To\:Find:}}$

• Average Speed = ?

$\Large\underline{\underline{\sf Formula\:Used:}}$

${\boxed{\boxed{\sf \pink{Average\: Speed=\dfrac{Total\: Distance}{Total\:Time}}}}}$

$\Large\underline{\underline{\sf Solution:}}$

Let ,

Distance from A to B is x

⛬ Total distance travelled = 2x

Time

$\sf{t_1=\dfrac{s_1}{v_1}}$

$\implies{\sf t_1=\dfrac{x}{20} }$

$\implies{\sf t_2=\dfrac{s_2}{v_2}}$

$\implies{\sf t_2=\dfrac{x}{30}}$

Total time t = $\sf{t_1+t_2}$

$\implies{\sf t =\dfrac{x}{20}+\dfrac{x}{30} }$

$\implies{\sf t=\dfrac{30x+20x}{20×30} }$

$\implies{\sf t=\dfrac{50}{600} }$

$\Large{\sf Average \: Speed=\dfrac{Total\: Distance}{Total\: Time} }$

$\implies{\sf v_{av}= \dfrac{2x}{\dfrac{50x}{600}}}$

$\implies{\sf v_{av}=24\:km/h }$

$\Large\underline{\underline{\sf Answer:}}$

⛬ The average speed of the car for the whole journey is 24 km/h