Now popular variable speed bicycles are equipped with several gears with different numbers of teeth on the drive shaft and the rear axle respectively. Different matching gears are connected by chains, and several gears with different speeds are obtained through different transmission ratios. There are 3 gears on the driving shaft of "Hope" variable speed bicycle, the number of teeth is 48, 36, 24 respectively; there are 4 gears on the rear axle, the number of teeth are 36, 24, 16, 12 respectively. Q: How many different speeds does this speed change car have?
现在流行的变速自行车，在主动轴和后轴分别安装了几个齿数不同的齿轮．用链条连接不同搭配的齿轮，通过不同的传动比获得若干挡不同的车速．"希望牌"变速自行车主动轴上有3个齿轮，齿数分别是48，36，24；后轴上有4个齿轮，齿数分别是36，24，16，12．问：这种变速车一共有多少挡不同的车速？
<gadget id="calculator">3 * 4</gadget>
<output>12</output>

<gadget id="calculator">12 - 4</gadget>
<output>8</output>

<result>8</result>