For a barrel of oil, (4/5) kilograms are used for the first time, and 0.9 kilograms are used for the second time, and (3/4) kilograms are left. How many kilograms does this barrel of oil originally weigh?
一桶油，第一次用去(4/5)千克，第二次用去0.9千克，还剩(3/4)千克，这桶油原来重多少千克？
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">(4/5) + 0.9 + (3/4)</gadget>
<output>2.45</output>

<result>2.45</result>