A canteen bought 7 new barrels of oil, and each barrel took out 40 kilograms of oil, so the remaining oil is only as much as the original 3 barrels. Excuse me, how many kilograms does each barrel of oil weigh?
某食堂新买了7桶油，且每桶油中各拿出40千克油，则剩下的油只有原来3桶那么多．请问，原来每桶油重多少千克？
<gadget id="calculator">7 - 3</gadget>
<output>4</output>

<gadget id="calculator">40 / 4</gadget>
<output>10</output>

<gadget id="calculator">7 * 10</gadget>
<output>70</output>

<result>70</result>