Dad bought a big cake, Lan Lan ate the cake (2/5), and mother ate the cake (1/5). What percentage of this cake did Mom eat less than Lan Lan?
爸爸买回来一个大蛋糕，兰兰吃了蛋糕的(2/5)，妈妈吃了蛋糕的(1/5)．妈妈比兰兰少吃了这个蛋糕的几分之几？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(2/5) - (1/5)</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>