The distance between the two places is 900 meters. A and B walk in the same direction at the same time and on the same place. A walks 80 meters per minute, and B walks 100 meters per minute. When B reaches the goal, he returns immediately and meets A. How many minutes did it take from departure to encounter?
两地相距900米，甲、乙二人同时、同地向同一方向行走，甲每分钟走80米，乙每分钟走100米，当乙到达目标后，立即返回，与甲相遇，两人从出发到相遇共经过多少分钟？
<gadget id="calculator">100 + 80</gadget>
<output>180</output>

<gadget id="calculator">2 / 180</gadget>
<output>1/90 = around 0.011111</output>

<gadget id="calculator">900 * (1/90)</gadget>
<output>10</output>

<result>10</result>