For a barrel of oil, (3/5) kg is used for the first time, and 0.9 kg is used for the second time, leaving (1/2) kg. How many kilograms does this barrel of oil weigh?
一桶油，第一次用去(3/5)千克，第二次用去0.9千克，还剩(1/2)千克．这桶油原重多少千克？
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(3/5) + 0.9 + (1/2)</gadget>
<output>2</output>

<result>2</result>