kind of exercise book can buy 4 copies for 5 yuan, how much does it cost to buy 10 copies of this kind of exercise book.
一种练习本5元可以买4本，购买10本这种练习本需要多少元．
<gadget id="calculator">5 / 4</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">(5/4) * 10</gadget>
<output>25/2 = around 12.5</output>

<result>25/2 = around 12.5</result>