The school plans to build a rectangular garden with a fence around the garden. During the actual construction, the length was shortened (1/5), which is exactly 4 meters shorter than the plan. To keep the garden area unchanged, the width becomes 15 meters. Now How many meters long to prepare the fence.
学校计划做一个长方形花园，在花园四周围上栅栏，实际施工时把长缩短了(1/5)，正好比计划缩短了4米，要使花园面积不变，这样宽变为15米，现在要准备栅栏多少米长．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">4 / (1/5)</gadget>
<output>20</output>

<gadget id="calculator">20 - 4</gadget>
<output>16</output>

<gadget id="calculator">16 + 15</gadget>
<output>31</output>

<gadget id="calculator">31 * 2</gadget>
<output>62</output>

<result>62</result>