2 boxes of apples weigh 20 kg, and 20% of them have been eaten. How many kg have been eaten?
2箱苹果重20千克，已经吃掉了20%，已经吃掉了多少千克？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">20 * (1/5)</gadget>
<output>4</output>

<result>4</result>