A barrel of oil, (1/5) kg is used for the first time, (2/5) kg is used for the second time, and (3/5) kg is left. How many kilograms does this barrel of oil weigh?
一桶油，第一次用去(1/5)千克，第二次用去(2/5)千克，还剩(3/5)千克．这桶油原重多少千克？
<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">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(1/5) + (2/5) + (3/5)</gadget>
<output>6/5 = around 1.2</output>

<result>6/5 = around 1.2</result>