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Problem of the day 14.7.09

with 12 comments


Given that 1025/1024=1.0009765625, find the sum of the digits of 510?

(a)  36       (b) 40    (c) 50   (d) 102   (e) 41

Written by Implex

July 14, 2009 at 1:22 pm

12 Responses

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  1. “the sum of the digits should leave 4 as the remainder on division by 9”

    anonymous

    July 14, 2009 at 6:10 pm

  2. Nicely done, this is the method I was looking for!

    Rahul

    July 14, 2009 at 7:42 pm

  3. guys could you elaborate on the method ?

    Hari

    July 15, 2009 at 4:57 am

    • First one is 5^10 gives a remainder 4 on division by 9. only one option gives the same. Hint: Whenever we talk about digit sum, think of modulo 9.

      Second 1025/1024-1=1/2^10=0.0009675625

      Hence 5^10=10^10/1024=9765625
      hence sum of digits is 40.

      Rahul

      July 15, 2009 at 10:10 am

  4. thanx a lot ..buddies ..for d xplanation

    anup

    July 15, 2009 at 4:34 pm

    • Rahul…it is always required ro see in terms of 9…

      Prateek

      July 15, 2009 at 5:47 pm

      • it helps to think in terms of modulo 9
        as divisibility rule of 9 talks about sum of digits

        Rahul

        July 15, 2009 at 5:50 pm

  5. Hey rahul can u even tell me how to prepare for DI and Verbal part..in terms of CAt

    Prateek

    July 15, 2009 at 5:53 pm

  6. Thnx man…

    Hari

    July 15, 2009 at 6:47 pm

  7. hey…u posted a hint above..
    Hint: Whenever we talk about digit sum, think of modulo 9.
    pl could u elaborate on that..thnkss:)

    Sam

    July 17, 2009 at 9:31 am

  8. I have explained in the comment above yours

    Rahul

    July 23, 2009 at 8:15 am


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