Car A and car B drive oppositely from two places 324 kilometers apart at the same time, and meet each other in 3.6 hours. The ratio of the speeds of cars A and B is 4:5, find the speed of car B.
甲、乙两车同时从相距324千米的两地相对开出，3.6小时相遇．甲、乙两车速度的比是4：5，求乙车的速度．
<gadget id="calculator">324 / 3.6</gadget>
<output>90</output>

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

<gadget id="calculator">5 / 9</gadget>
<output>5/9 = around 0.555556</output>

<gadget id="calculator">90 * (5/9)</gadget>
<output>50</output>

<result>50</result>