Price Plus 1/2 Price

Date: 12/05/2001 at 21:20:41
From: Michelle 
Subject: Math problems - critical thinking

A puzzle book costs 5.00 plus one-half of its price. How much does 
the puzzle book cost? (It is not $7.50.)

Date: 12/05/2001 at 22:06:19
From: Doctor Ian
Subject: Re: Math problems - critical thinking

Hi Michelle,

This is one of those cases where variables come in really handy. 

We're looking for a price. We don't know what it is, but we can give 
it a name:  P.  

  The price of the book is $5 plus one-half the price.

 \___________________/            \________________/
           P             =  5  +       (1/2)*P

Can you take it from here?

(Note that, as if often the case in puzzles like this, there is a way 
to 'see' the answer without doing any computations at all.  If the 
book costs $5 plus 1/2 its cost... then $5 must be the _other_ half of 
its cost.)  

- Doctor Ian, The Math Forum
  http://mathforum.org/dr.math/