If (1/5) of a bottle of oil is used, and (1/5) kg is poured in, it will be exactly the same weight as the original one. How many kilograms does this bottle of oil have?
一瓶油用去它的(1/5)，又倒入(1/5)千克后恰好和原来同样重，这瓶油原来多少千克．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

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

<result>1</result>