Difference between revisions of "2003 AMC 12B Problems/Problem 8"

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<cmath>\clubsuit(\clubsuit(x)) = a + b = 3</cmath>
 
<cmath>\clubsuit(\clubsuit(x)) = a + b = 3</cmath>
  
Clearly the only two digit numbers whose digits sum to <math>3</math> are <math>12, 21,</math> and <math>30</math>, thus the answer is <math>3 \Rightarrow \text (A)</math>
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Clearly <math>\\clubsuit(x)</math> can only be <math>3, 12, 21,</math> or <math>30</math> and only <math>3</math> and <math>30</math> are possible to have two digits sum to.
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If <math>\\clubsuit(x)</math> is \Rightarrow \text (E)$

Revision as of 23:32, 19 December 2012

Let $a$ and $b$ be the digits of $x$,

\[\clubsuit(\clubsuit(x)) = a + b = 3\]

Clearly $\\clubsuit(x)$ can only be $3, 12, 21,$ or $30$ and only $3$ and $30$ are possible to have two digits sum to.

If $\\clubsuit(x)$ is \Rightarrow \text (E)$