The ratio of the teeth of two circular gears meshing with each other is 9:7, the large gear has 36 teeth, and how many teeth does the small gear have.
两个相互咬合的圆形齿轮的齿数之比是9：7，其中大齿轮有36个齿，小齿轮有多少个齿．
<gadget id="calculator">36 / 9</gadget>
<output>4</output>

<gadget id="calculator">4 * 7</gadget>
<output>28</output>

<result>28</result>