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| Math Central | Quandaries & Queries |
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Question from Lloyd, a student: The sum of digits of a certain 2 digit number is 7. |
Hi Lloyd,
Suppose the units digit of the number is $n$ and the tens digit is $m,$ then the number is $10m + n.$
You know that $m + n = 7.$
What is the number obtained if you reverse the digits? This number is $9$ more than the original number. This gives you a second equation in $m$ and $n.$ Solve the pair of equations for $m$ and $n.$
Penny
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