There are 9 students playing ping-pong on two ping-pong tables, one for singles and one for doubles. They played from 11:30 am to 1:00 pm, how many minutes did each person play on average?
有9位同学在两张乒乓台上打乒乓，一张是单打，一张是双打．他们从上午11：30玩至下午1：00，平均每人打了多少分钟．
<gadget id="calculator">90 / 9</gadget>
<output>10</output>

<gadget id="calculator">6 * 10</gadget>
<output>60</output>

<result>60</result>