Multiplication Riddle

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Can you find three consecutive odd numbers that gives total 1,287 when multiplied together?

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  • 2 Answer(s)

    9, 11, 13 (9 * 11 * 13 = 1287)

    Deduction:

    1. We know that 10*10*10 = 1000, fairly close to the target value of 1287. Thus, the required numbers should be somewhere close to 10.
    2. ‘The consecutive odd numbers’ CAN’T include a number which is multiple of 5, because an odd-number multiple of 5 will ALWAYS have 5 as the last digit, wheres we require 7.
    3. The only possible sequences of three consecutive odd numbers without involving ‘5’ is such that the numbers must end as 7, 9 and 1 OR 9, 1 and 3. ([1,3,5], [3,5,7] and [5,7,9] can’t be considered as all of them contain ‘5’ as a member.)
    4. The ‘answer triplet’ CAN’T be such that they end in [7,9.1]  because the product of such a set will have last digit as 3, whereas the target is 7. So, from (3) above, the numbers must be ending 9, 1, 3.

    From the above, we conclude that the only possible combination is 9, 11, 13.

    Viji_Pinarayi Expert Answered on 30th March 2018.
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    Yes. 9, 11 and 13. Numbers that average slightly more than 10, where 10*10*10 = 1000..

    bonanova Scholar Answered on 16th April 2018.
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