A barrel is filled with half a barrel of oil, and after pouring out (2/5) of the oil, there is still 15kg left. How many kilograms can this barrel of oil hold?
一只桶装了半桶油，倒出油的(2/5)后，还剩15kg．这桶油能装油多少千克？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

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

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

<gadget id="calculator">(1/2) - (1/5)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">15 / (3/10)</gadget>
<output>50</output>

<result>50</result>