An isosceles triangle is formed by a length of 90 cm wire. The length ratio of one waist to the base is 2:1. What is the length of the base of this triangle in cm?
用一段长90厘米的铁丝围成一个等腰三角形，一条腰与底边的长度比是2：1，这个三角形底边的长是多少厘米？
<gadget id="calculator">2 / 2 / 1</gadget>
<output>1</output>

<gadget id="calculator">2 + 2 + 1</gadget>
<output>5</output>

<gadget id="calculator">2 / 2 / 1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">90 * (1/5)</gadget>
<output>18</output>

<result>18</result>