Xiaoqiang and his grandfather run to the playground every morning for running exercise. Xiaoqiang takes 4 minutes for one lap, and grandpa takes 20 minutes for one lap. If they both start at the same place at the same time, how long will it take for Xiaoqiang to catch up with grandpa for the first time?
小强和爷爷每天早上在操场跑到进行跑步锻炼，小强一圈要4分钟，爷爷一圈要20分钟，如果两人同时同地出发，小强第一次追上爷爷，用多少时间？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/4) - (1/20)</gadget>
<output>1/5 = around 0.2</output>

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

<result>5</result>