Two gears mesh with each other. The large gear has 60 teeth and rotates at 90 revolutions per minute. The small gear rotates three times as fast as the large gear. How many teeth does the small gear have?
两个互相咬合的齿轮，大齿轮有60个齿，每分钟转90转，小齿轮每分钟的转数是大齿轮的三倍，小齿轮有多少个齿？
<gadget id="calculator">60 * 90</gadget>
<output>5_400</output>

<gadget id="calculator">90 * 3</gadget>
<output>270</output>

<gadget id="calculator">5_400 / 270</gadget>
<output>20</output>

<result>20</result>