A circular runway is 4.5 cm drawn on a map with a scale of 1:20000. A and B run in opposite directions at the same place and meet each other in 5 minutes. The speed ratio of A and B is 5:4. How many minutes does it take B to run alone?
一条环形跑道画在比例尺为1：20000地图上是4.5厘米，甲乙两人在同一地点往相反的方向跑，5分钟相遇，甲乙的速度比是5：4，独自跑完全程乙要多少分钟？
<gadget id="calculator">1 / 20_000</gadget>
<output>1/20_000 = around 0.00005</output>

<gadget id="calculator">4.5 / (1/20_000) / 100 / 5</gadget>
<output>180</output>

<gadget id="calculator">5 + 4</gadget>
<output>9</output>

<gadget id="calculator">4 / 9</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">180 * (4/9)</gadget>
<output>80</output>

<gadget id="calculator">4.5 / (1/20_000) / 100 / 80</gadget>
<output>11.25</output>

<result>11.25</result>