The perimeter of a cylinder expanded sideways is 61.68 cm. If the height is known to be twice the diameter of the base, what is the diameter of the base of the cylinder in centimeters? (π takes 3.14)
一个圆柱的侧面展开图的周长是61.68厘米．己知高是底面直径的2倍，这个圆柱的底面直径是多少厘米．(π取3.14)
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