A cylindrical oil barrel is filled with oil, and there are 78.5 liters left when the oil is poured out (1/6). It is known that the height of the oil barrel is 6.28 decimeters. What is the area of the bottom of the oil barrel in square decimeters?
一个圆柱油桶，里面装满了油，把油倒出(1/6)还剩78.5升，已知油桶高是6.28分米，求油桶的底面积是多少平方分米？
<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 - (1/6)</gadget>
<output>5/6 = around 0.833333</output>

<gadget id="calculator">78.5 / (5/6) / 6.28</gadget>
<output>15</output>

<result>15</result>