If 10 flags are inserted on one side of a 90-meter-long runway, what is the average distance between two adjacent flags?
在长90米的跑道一侧插上10面旗子，(两端都插)平均每相邻两面旗子间的距离是多少．
<gadget id="calculator">10 - 1</gadget>
<output>9</output>

<gadget id="calculator">90 / 9</gadget>
<output>10</output>

<result>10</result>