When four cylinders of the same size are assembled into a large cylinder with a height of 40 cm, the surface area is reduced by 72 square centimeters. What is the volume of the original small cylinder in cubic centimeters?
四个同样大小的圆柱拼成一个高为40厘米的大圆柱时，表面积减少了72平方厘米，原来小圆柱的体积是多少立方厘米．
<gadget id="calculator">72 / 6</gadget>
<output>12</output>

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

<gadget id="calculator">12 * 10</gadget>
<output>120</output>

<result>120</result>