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Add age word problem hints accidentally nixed earlier

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1 parent 700fdb7 commit b25e69766853e7ef757c03813f9e1493962bdcf2 @spicyj spicyj committed Jun 1, 2011
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  1. +5 −0 exercises/age_word_problems.html
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5 exercises/age_word_problems.html
@@ -115,6 +115,11 @@
<div class="solution"><var>A * B * (C - 1) / (C - A)</var></div>
<div class="hints">
+ <p>Let <var>person(1)</var>'s age be <code><var>personVar(1)</var></code>.</p>
+ <p>We know <var>person(2)</var> is <code>1/<var>A</var></code> as old as <var>person(1)</var>, so <var>person(2)</var>'s age can be written as <code><var>personVar(1)</var> / <var>A</var></code>.</p>
+ <p><var>B</var> years ago, <var>person(1)</var> was <code><var>personVar(1)</var> - <var>B</var></code> years old and <var>person(2)</var> was <code><var>personVar(1)</var> / <var>A</var> - <var>B</var></code> years old.</p>
+ <p>At that time, <var>person(1)</var> was <var>C</var> times as old as <var>person(2)</var>, so we can write <code><var>personVar(1)</var> - <var>B</var> = <var>C</var> (<var>personVar(1)</var> / <var>A</var> - <var>B</var>)</code>.</p>
+ <p>Expand: <code><var>personVar(1)</var> - <var>B</var> = <var>fraction(C, A)</var> <var>personVar(1)</var> - <var>C * B</var></code>.</p>
<p>Solve for <code><var>personVar(1)</var></code> to get <code><var>fraction(C - A, A)</var> <var>personVar(1)</var> = <var>B * (C - 1)</var></code>; <code><var>personVar(1)</var> = <var>fraction(A, C - A)</var> \cdot <var>B * (C - 1)</var> = <var>A * B * (C - 1) / (C - A)</var></code>.</p>
</div>
</div>

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