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10th Class Mathematics Related to Competitive Exam Question Bank Algebra

  • question_answer
    Three bells, toll at intervals of 36 sec, 40 sec and sec respectively. They start ringing toll at particular time. They next toll together after

    A)  18 minutes      

    B)         12 minutes  

    C)  6 minutes       

    D)         24 minutes

    Correct Answer: B

    Solution :

     Let us first find \[L.C.M.\] of \[36,\,\,40,\,\,48\]
    \[2\] \[36,\,\,40,\,\,38\]
    \[2\] \[18,\,\,20,\,24\]
    \[2\] \[9,\,\,10,\,\,12\]
    \[3\] \[9,\,\,5,\,\,6\]
    \[3,\,\,5,\,\,2\]
    \[\therefore \]\[L.C.M.\]of\[36,\,\,40,\,\,48\]\[=2\times 2\times 2\times 3\times 3\times 5\times 2\]\[=720\,\,\sec \]. Hence, the next time the three bells will toll together after\[720\,\,\sec =12\,\,\min \].


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