Answer This Math Question

math teacherAnswer This Math Question - 12 July

A 3 digit number is such that it's unit digit is equal to the product of the other two digits which are prime. Also, the difference between it's reverse and itself is 396.
What is the sum of the three digits?

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14 comments:

  1. It's 155 - There are only 12 possible combinations of numbers where the first 2 digits are primes and the multiplication result is lower than 10

    Here's the full list of possible Numbers
    Digit 1 Digit 2 Digit 3 Number Reverse Diff
    1 1 1 111 111 0
    1 2 2 122 221 99
    1 3 3 133 331 198
    1 5 5 155 551 396
    1 7 7 177 771 594
    2 1 2 212 212 0
    2 2 4 224 422 198
    2 3 6 236 632 396
    2 4 8 248 842 594
    3 1 3 313 313 0
    3 2 6 326 623 297
    3 3 9 339 933 594

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  2. 11

    The question is the sum of it's 3 digits. So possible choices are 155. But also 236. There all add to 11

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  3. 11

    The question is the sum of it's 3 digits. So possible choices are 155. But also 236. There all add to 11

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  4. Digit at 100's place = x
    digit at 10's place = y
    digit at unit place = xy ( a single digit)

    value of number is : 100x+10y+xy

    value of reverse number : 100xy +10y+ x

    according to problem, difference is 396

    so, 99xy - 99x = 396

    after solving, x = 2, y = 3

    actual number is : 236
    reverse of number is : 632

    sum of three digits is : 11

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  5. Answer is 11.The number is 236 not 155 as 1 is neither prime nor composite.

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  6. i think 236 is wrong ans 6 is not a prime.. its 155 only....

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  7. 1 is not a prime no...wrong quest. !

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    Replies
    1. chk solution and den comment
      http://solution-dailybrainteaser.blogspot.com/2012/07/answer-this-math-question.html

      Delete
  8. Oh I just read it wrong it is 236

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  9. muhammad shehzar chohanAugust 3, 2013 at 2:59 AM

    very bad question

    ReplyDelete