The cafeteria bought 7 barrels of oil, each of which is of equal quality. If 30.4 kilograms of oil are removed from each barrel, the remaining oil will have the same mass as the original 3 barrels. How many kilograms does a barrel of oil weigh?
食堂买来7桶油，每桶油质量相等．如果从每桶油中各取出30.4千克油，则剩下的油与原来3桶油的质量相等．原来每桶油重多少千克？
<gadget id="calculator">7 - 3</gadget>
<output>4</output>

<gadget id="calculator">7 / 4</gadget>
<output>7/4 = around 1.75</output>

<gadget id="calculator">30.4 * (7/4)</gadget>
<output>53.2</output>

<result>53.2</result>