๐Ÿ“ข Too many exams? Donโ€™t know which one suits you best? Book Your Free Expert ๐Ÿ‘‰ call Now!

    Question

    Four bells start ringing together

    at 9:00 am. They ring at intervals of 15 seconds, 20 seconds, 30 seconds, and 40 seconds. At what time will they ring together again?
    A 9:20 am Correct Answer Incorrect Answer
    B 9:00 am Correct Answer Incorrect Answer
    C 9:02 am Correct Answer Incorrect Answer
    D None of these Correct Answer Incorrect Answer

    Solution

    ATQ,

    All the four bells ring together at 9:00 am, and after that, they ring at different intervals. The time after which they will ring together again is the LCM of [15, 20, 30, 40].

    15 = 3ยน ร— 5ยน 20 = 2ยฒ ร— 5ยน 30 = 2ยน ร— 3ยน ร— 5ยน 40 = 2ยณ ร— 5ยน

    So, the required LCM = 2ยณ ร— 3ยน ร— 5ยน = 8 ร— 3 ร— 5 = 120 seconds = (120/60) = 2 minutes. So, after 2 minutes from 9:00 am, they will ring together again, i.e., at 9:02 am.

    Practice Next
    More Time Questions

    Relevant for Exams:

    ask-question