Primes and Number RiddlesDate: 4/15/96 at 21:17:0 From: Anonymous Subject: Pre Algebra: Finding primes as the result of solving number riddles I am having difficulty understanding this riddle. Please help me to find the proper method to solve this and future riddles like it. Thanks and here is the problem as it appears in its entirety. Three different one-digit primes Produce me, if you're using times; If my digits you add, Another prime will be had. Two answers - and nothing else rhymes. Thank you very much for your assistance! Date: 4/22/96 at 20:19:12 From: Doctor Joshua Subject: Re: Pre Algebra: Finding primes as the result of solving number riddles Hi! By process of elimination, there are only four one-digit primes: 2,3,5, and 7. Multiplying any three of these together: 2X3X5 = 30 Sum of digits = 3, this works! 2X3X7 = 42 Sum of digits = 6 2X5X7 = 70 Sum of digits = 7, this works as well. 3X5X7 = 105 Sum of digits = 6 So the answers to the riddle are 30 and 70. -Doctor Joshua, The Math Forum Check out our web site! http://mathforum.org/dr.math/ |
Search the Dr. Math Library: |
[Privacy Policy] [Terms of Use]
Ask Dr. Math^{TM}
© 1994-2013 The Math Forum
http://mathforum.org/dr.math/