Races and games


  1. A’s speed is 138 times of B’s. In a race A gives B a start of 300 m. How long should the race course be so that both reach the winning post simultaneously?









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    A’s speed : B’s speed = 112 : 1
    = 32 : 1
    = 3 : 2
    It means that in a race of 3 m, A gains (3 - 2).
    = 1 m over B. 1 m is gained by A in a race of 3 m.

    Correct Option: B

    A’s speed : B’s speed = 112 : 1
    = 32 : 1
    = 3 : 2
    It means that in a race of 3 m, A gains (3 - 2).
    = 1 m over B. 1 m is gained by A in a race of 3 m.
    ∴ 300 m is gained by A in a race of = 31 × 300 = 900 m.


  1. A and B run a 5 Km race on a round course of 400 m. If their speeds be in the ratio 5 : 4, then how often does the winner pass the other?









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    When A makes 5 rounds, B makes 4 rounds.
    In order to pass each other, the difference in number of rounds made by each must be one.
    Here, A passes B each time, when A makes 5 rounds.
    Distance covered by A in 5 rounds = 5 * 400 / 100 × = 2 Km.

    Correct Option: D

    When A makes 5 rounds, B makes 4 rounds.
    In order to pass each other, the difference in number of rounds made by each must be one.
    Here, A passes B each time, when A makes 5 rounds.
    Distance covered by A in 5 rounds = 5 * 400 / 100 × = 2 Km.
    In covering 2 Km, A passes B 1 time.
    ∴ In covering 5 Km, A passes B
    = 5 / 2 = 212 times.



  1. In a Km race A can beat B by 80 m and B can beat C by 60 m. In the same race, A can beat C by :









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    While A runs 1000 m, B runs 1000 - 80 = 920 m and
    while B runs 1000 m, C runs 1000 - 60 = 940 m.
    ∴ While B runs 920 m; C runs 940 × 920 / 1000 = 4324 / 5 m

    Correct Option: A

    While A runs 1000 m, B runs 1000 - 80 = 920 m and
    While B runs 1000 m, C runs 1000 - 60 =940 m.
    ∴ While B runs 920 m; C runs
    940 / 1000 × 920 = 4324 / 5 m
    ∴ While B runs 920 m; C runs 940 × 920 / 1000 = 4324 / 5 m
    ∴ While A runs 1000 m, C runs 4324 / 5 m
    ∴ A can beat C by 1000 - 4324 / 5 = 676 / 5 = 13515 m.


  1. A and B runs a Km race. If A gives B a start of 50 m, A wins by 14 sec and, if A gives B a start of 22 sec Km, B wins by 20 m. The time taken by A to run a Km is:









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    Let, times (in sec) taken by A and B to run a Km, be P and Q, respectively.
    When B gets a start of 50 m, B runs.
    1000 - 50 = 950 m while A runs 1000 m.

    Correct Option: A

    Let, times (in sec) taken by A and B to run a Km, be P and Q, respectively.
    When B gets a start of 50 m, B runs.
    1000 - 50 = 950 m while A runs 1000 m.
    ∴ 950 / 100 Q - P = 14,
    i.e., 0.95Q - P = 14 …(1)
    and, when B gets a start of 22 seconds, A runs for (Q - 22) seconds, while B runs for Q seconds.
    ∴ 1000 - 1000 / P (Q - 22) = 20
    i.e., 50Q - 49P = 1100. …(2)
    Multiplying Eq. (1) by 49 and subtract from Eq. (2)
    3.45Q = 414
    ∴ Q= 120 sec.
    ∴ from (1)
    ⇒ P = 0.95 × 120 - 14 = 100 seconds.



  1. A can run 500m in 30 seconds and B in 35 seconds. How many meter start can A give to B in a Km race so that the race may end in a dead-heat?









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    Time taken by A to run 1 Km = 30 × 2 = 60 seconds.
    Time taken by B to run 1 Km = 35 × 2 = 70 seconds.
    A can give B a start of (70 - 60) = 10 seconds.

    Correct Option: C

    Time taken by A to run 1 Km = 30 × 2 = 60 seconds.
    Time taken by B to run 1 Km = 35 × 2 = 70 seconds.
    A can give B a start of (70 - 60) = 10 seconds.
    In 35 sec B runs 500 m
    ∴ In 10 sec B runs = 500 × 10 / 35 = 1000 / 7 = 14267 meters
    So, A can give B a start of 14267 meters in a Km race.