If the perimeter of an isosceles triangle is 70 cm and the ratio of the two sides is 1:3, what is the length of one of its sides in cm?
一个等腰三角形的周长是70厘米，其中两条边的比是1：3，那么它的一条腰长多少厘米
<gadget id="calculator">1 + 3 + 3</gadget>
<output>7</output>

<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">70 * (3/7)</gadget>
<output>30</output>

<result>30</result>