A barrel of oil, pour out (3/10) kilograms on average each time, pour 4 times, and there is still (9/10) kilograms in the barrel, how many times will it take to pour out all the oil in the barrel?
一桶油，平均每次倒出(3/10)千克，倒了4次，桶里还剩下(9/10)千克，一共要倒多少次才能把这桶油全部倒完？
<gadget id="calculator">9 / 10</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">(9/10) / (3/10)</gadget>
<output>3</output>

<gadget id="calculator">3 + 4</gadget>
<output>7</output>

<result>7</result>