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    jayachandrab's Avatar
    jayachandrab Posts: 2, Reputation: 1
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    #1

    Dec 26, 2009, 03:22 AM
    .37 A cyclist travels for 2 hours at 20 km/hr, next 1 hour at 15Km/ hr and at 10 km/h
    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.
    Clough's Avatar
    Clough Posts: 26,677, Reputation: 1649
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    #2

    Dec 26, 2009, 03:23 AM
    Hi, jayachandrab!

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

    Thanks!
    jayachandrab's Avatar
    jayachandrab Posts: 2, Reputation: 1
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    #3

    Dec 26, 2009, 03:24 AM
    Quote Originally Posted by jayachandrab View Post
    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.
    Answer=Total distance/total time

    40+15+20/5=15
    Random.12am's Avatar
    Random.12am Posts: 3, Reputation: 1
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    #4

    Dec 26, 2009, 03:27 AM

    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.
    Alty's Avatar
    Alty Posts: 28,317, Reputation: 5972
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    #5

    Dec 26, 2009, 08:13 PM
    Quote Originally Posted by jayachandrab View Post
    Answer=Total distance/total time

    40+15+20/5=15
    Thanks for the info. Why did you ask if you already knew the answer?
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