If a certain juvenile book is sold at the original price, each book sold will make a profit of 0.36 yuan; if it is sold at a reduced price, the sales volume will double and the profit will increase by 0.5 times.
某种少年读物，如果按原定价格销售，每售一本，获利0.36元；现在降价销售，结果售书量增加一倍，获利增加0.5倍，每本书售价降价多少元．
<gadget id="calculator">0.36 * 2</gadget>
<output>0.72</output>

<gadget id="calculator">0.36 * 1.5</gadget>
<output>0.54</output>

<gadget id="calculator">0.72 - 0.54</gadget>
<output>0.18</output>

<gadget id="calculator">0.18 / 2</gadget>
<output>0.09</output>

<result>0.09</result>