Cars A and B start from two places and drive toward each other. A travels 40 kilometers per hour, and B travels 60 kilometers per hour. After three hours, they meet. How many hours does it take for B to travel alone?
甲乙两车从两地出发相向而行，甲每小时行40千米，乙每小时行60千米，经过三小时相遇．乙单独行完全程要几小时？
<gadget id="calculator">40 + 60</gadget>
<output>100</output>

<gadget id="calculator">3 / 60</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">100 * (1/20)</gadget>
<output>5</output>

<result>5</result>