Q.37 A cyclist travels for 2 hours at 20 km/hr, next 1 hour at 15Km/ hr and at 10 km/hr for the nuxt two hours. What will be his average speed in km/hr?
(A) 9 (B) 15
© 20 (D) 45
(E) None of these.

Hi, jayachandrab!

Are you looking for a direct answer or how to come up with the answer yourself, please?

Thanks!

Quote:

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Originally Posted by jayachandrab

Q.37 A cyclist travels for 2 hours at 20 km/hr, next 1 hour at 15Km/ hr and at 10 km/hr for the nuxt two hours. What will be his average speed in km/hr?
(A) 9 (B) 15
© 20 (D) 45
(E) None of these.

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Answer=Total distance/total time

40+15+20/5=15

Hello,

First, you calculate the distance travelled. You know that

distance = speed x time. (equation 1)

I say "speed" rather than "velocity" because I assume direction is uniform in one dimension.

Anyway, for the first period where the cyclist is going at 20km/h, you have a distance of (20km/h x 2h = 40km) travelled. Similarly, for the next hour, the cyclist travels 15km, and finally 20km. Total distance is 40+15+20=75km. A manipulation of equation 1 yields:

speed = distance / time (equation 2)

And the total time is 5 hours. Therefore, the average speed is 75/5 = 15

Briefly, the answer is B.

Quote:

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Originally Posted by jayachandrab

Answer=Total distance/total time

40+15+20/5=15

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Thanks for the info. Why did you ask if you already knew the answer?