There is a toy car, the radius of the rear wheel is twice the radius of the front wheel. If the rear wheel turns 8 times, how many times does the front wheel turn?
有一种玩具车，后轮半径是前轮半径的2倍．如果后轮转动8圈，那么前轮转动多少圈．
<gadget id="calculator">2 * 2</gadget>
<output>4</output>

<result>4</result>