A bottle of oil is used for the first time (1/5), and the remaining (2/5) is used for the second time. At this time, there is still (1/5) kilogram in the bottle. How many kilograms does this bottle of oil have?
一瓶油第一次用去(1/5)，第二次用去余下的(2/5)，这时瓶内还剩(1/5)千克，这瓶油原有有多少千克？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<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">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(1/5) / (3/5) / (4/5)</gadget>
<output>5/12 = around 0.416667</output>

<result>5/12 = around 0.416667</result>