A cylinder with a surface area of 50 square centimeters has a base area of 15 square centimeters. If two such cylinders are put together to form a large cylinder, what is the surface area of the large cylinder in square centimeters?
一个表面积50平方厘米的圆柱体，底面积是15平方厘米，把2个这样的圆柱体拼成一个大圆柱体，这个大圆柱体的表面积是多少平方厘米．
<gadget id="calculator">15 * 2</gadget>
<output>30</output>

<gadget id="calculator">50 - 30</gadget>
<output>20</output>

<gadget id="calculator">50 + 20</gadget>
<output>70</output>

<result>70</result>