Question

solve please this question

Answer 1

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Let distance be d

Speed (1) = 20km/h

Time taken = distance / speed
= d/20

Speed (2) = 30km/h

Time = Distance/time
= d/30

Average speed = total distance /total time
=( d+d) /{(d/20)+(d/30)}
= 2d / (d/12)
=24d/ d
= 24

So, the average speed of the car was 24km/h

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Answer 2

Speed = Distance / Time taken

Distance = Speed × Time taken

Time taken = Distance / Speed

time taken while going to college = t

time taken when return to home = T

( while going to college) t= S/20 hr

( return to home ) T = S/ 30 hr

Total time taken by Akhil Ta = t + T

===> ( S/20 + S/30 )

===> 1/10 ( S/2 + S/3)

===> 1/10 ( 2S+3S/6)

===> 1/10 ( 5S/6)

===> 1/2 ( S/6)

===> S/12

Total distance = S( going ) + S( return) = 2S

....(route of going and return is same)

Average speed = Total distance dravelled / time taken

===> 2S/ S/12

===> 2×12S/S

===> 24 km/ hr

hence average speed is 24 km / hr of akhil' s car