The tram departure station sends out a tram every fixed time. Xiao Wang encounters an oncoming tram every 15 minutes while riding a bicycle. If Xiao Wang increases his speed by 20%, he will encounter an oncoming tram every 14 minutes. How many minutes is the difference between the departure time of two adjacent trams?
电车发车站每隔固定时间发出一辆电车，小王骑自行车每隔15分钟遇到一辆迎面开来的电车，如果小王车速提高20%，则每隔14分钟就遇到一辆迎面开来的电车，那么相邻两辆电车的发车时间相差多少分钟？
<gadget id="calculator">4 / 1</gadget>
<output>4</output>

<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">3 * 14</gadget>
<output>42</output>

<gadget id="calculator">42 / 4</gadget>
<output>21/2 = around 10.5</output>

<result>21/2 = around 10.5</result>