How many 20-yuan renminbi can be exchanged for 4 pieces of 50-yuan renminbi?
4张50元的人民币可以兑换多少张20元的人民币．
<gadget id="calculator">4 / 20</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">50 * (1/5)</gadget>
<output>10</output>

<result>10</result>