A piece of cake, Xiaoming ate (1/6), Xiaoqing ate the rest (2/5), how much did Xiaoqing eat this piece of cake.
一张饼，小明吃了(1/6)，小青吃了余下的(2/5)，小青吃了这张饼的多少．
<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 - (1/6)</gadget>
<output>5/6 = around 0.833333</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(5/6) * (2/5)</gadget>
<output>1/3 = around 0.333333</output>

<result>1/3 = around 0.333333</result>