cylindrical oil barrel is filled with soybean oil, and 30% of the soybean oil in the oil barrel is poured out, leaving 630 liters. If the bottom area of the oil barrel is 75 square decimeters, how many decimeters is the height of the oil barrel?
一个圆柱形油桶装满了豆油，把油桶内的豆油倒出30%，还剩630升．如果油桶的底面积是75平方分米，则油桶高多少分米？
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 - (3/10)</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">630 / (7/10)</gadget>
<output>900</output>

<gadget id="calculator">900 / 75</gadget>
<output>12</output>

<result>12</result>