A kind of exercise book is sold at half price. It used to cost 45 copies, but how many copies can you buy now?
一种练习本半价销售，原来买45本的钱，现在可以买多少本．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / (1/2)</gadget>
<output>2</output>

<gadget id="calculator">45 * 2</gadget>
<output>90</output>

<result>90</result>