There is a barrel filled with half a barrel of oil. After pouring out (2/5) of the oil, there is still 15 kilograms of oil left. How many kilograms of oil can this barrel hold?
有一只桶，装了半桶油，倒出油的(2/5)后，还剩15千克油，问这只桶能装油多少千克．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">15 / (3/5)</gadget>
<output>25</output>

<gadget id="calculator">25 * 2</gadget>
<output>50</output>

<result>50</result>