A barrel of oil, eat 3 kilograms, and there is still the whole barrel (4/5), what is the original kilogram of this barrel of oil?
一桶油，吃了3千克，还剩全桶的(4/5)，这桶油原有多少千克．
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">3 / (1/5)</gadget>
<output>15</output>

<result>15</result>