315 teachers and students in the fourth grade of Hope Primary School went on an outing. They took a total of 5 buses and 2 small buses. On average, each bus can hold 55 people. Find the average number of people that a small bus can carry.
希望小学四年级师生315人去郊游，共乘坐了5辆大客车和2辆小客车，平均每辆大客车可坐55人，求平均一辆小客车可乘坐多少人．
<gadget id="calculator">55 * 5</gadget>
<output>275</output>

<gadget id="calculator">315 - 275</gadget>
<output>40</output>

<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<result>20</result>