4 students played singles on a table tennis table for 60 minutes, how many minutes did each of them play on average?
4个同学在一张乒乓球台上单打60分钟，平均每人打了多少分钟？
<gadget id="calculator">60 / 4</gadget>
<output>15</output>

<gadget id="calculator">15 * 2</gadget>
<output>30</output>

<result>30</result>