There is a barrel of oil, (1/4) of the total amount is taken out for the first time, (2/5) of the total amount is taken out for the second time, and 7.5 kilograms more oil is taken out for the second time than the first time, how many kilograms is this barrel of oil?
有一桶油，第一次取出总数的(1/4)，第二次取出总数的(2/5)，第二次比第一次多取油7.5千克，这桶油有多少千克？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(2/5) - (1/4)</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">7.5 / (3/20)</gadget>
<output>50</output>

<result>50</result>