The ratio of a mobile phone signal transmitting and receiving tower buried underground to the part exposed to the ground is 3:18, and the buried part is 4 meters, so how many meters is the total length of the tower?
一个手机信号发射接收塔埋在地下与露出地面部分的比是3：18，埋在地下的部分是4米，那么这个塔的全长是多少米？
<gadget id="calculator">3 + 18</gadget>
<output>21</output>

<gadget id="calculator">3 / 21</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">4 / (1/7)</gadget>
<output>28</output>

<result>28</result>