There is a willow tree planted every 9 meters on one side of the road. Xiao Liang saw 501 trees after 5 minutes from seeing the first willow tree in a car. How many kilometers does the car drive per hour?
马路一边每隔9米栽有一棵柳树，小亮乘汽车从看到第一棵柳树起，经过5分钟看到501棵树，那么汽车每小时行驶多少千米？
<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">4.5 / (1/12)</gadget>
<output>54</output>

<result>54</result>