A project can be completed in 10 days by A alone. The ratio of work efficiency between A and B is 1:2. How many days will it take for B to do this project alone?
一项工程，甲独做10天完成，甲和乙工作效率的比是1：2，乙独做这项工程需要多少天．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 10 / (1/2)</gadget>
<output>1/5 = around 0.2</output>

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

<result>5</result>