If it takes 10 seconds to strike 3 times, how many seconds will it take to strike 9 times if the interval between each strike is equal?
钟敲3下要10秒钟，如果每敲一下间隔的时间相等，那么敲9下要多少秒钟．
<gadget id="calculator">3 - 1</gadget>
<output>2</output>

<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">9 - 1</gadget>
<output>8</output>

<gadget id="calculator">5 * 8</gadget>
<output>40</output>

<result>40</result>