The cafeteria buys some rice, and after eating half of it, buys back 270kg. The rice at this time is equivalent to (4/5) of the original total amount of rice. How many kilograms of rice did you buy?
食堂买回一些大米，吃了一半后，又买回270kg，这时的大米相当于原来大米总数的(4/5)，原来买来大米多少千克？
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

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

<gadget id="calculator">(4/5) - (1/2)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">270 / (3/10)</gadget>
<output>900</output>

<result>900</result>