Difference between revisions of "2014 UNM-PNM Statewide High School Mathematics Contest II Problems/Problem 5"
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== Solution == | == Solution == | ||
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What you have to realize is that the sum of the digits of a number is the number <math>\pmod{9}</math>. We can prove this right now. | What you have to realize is that the sum of the digits of a number is the number <math>\pmod{9}</math>. We can prove this right now. | ||
\begin{equation} | \begin{equation} | ||
Revision as of 22:24, 27 September 2019
Problem
is written on the blackboard. The sum of its digits is calculated. Then the sum of the
digits of the result is calculated and so on until we have a single digit. If 
, what
is this digit?
Solution
This problem needs a solution. If you have a solution for it, please help us out by adding it.
What you have to realize is that the sum of the digits of a number is the number 
. We can prove this right now.
\begin{equation}
\end{equation}
See also
| 2014 UNM-PNM Contest II (Problems • Answer Key • Resources) | ||
| Preceded by Problem 4 |
Followed by Problem 6 | |
| 1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 | ||
| All UNM-PNM Problems and Solutions | ||
