A project is completed in 30 days by A alone, and completed by B in 40 days alone. Now the two work together and complete it in 25 days, during which A rests twice as many days as B. How many days does B rest?
一项工程，甲单独做30天完成，乙单独做40天完成，现在两人一起做，共用25天完成，其间甲休息的天数是乙休息天数的2倍．乙休息几天？
<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">1 / 40</gadget>
<output>1/40 = around 0.025</output>

<gadget id="calculator">(1/30) + (1/40)</gadget>
<output>7/120 = around 0.058333</output>

<gadget id="calculator">25 * (7/120)</gadget>
<output>35/24 = around 1.458333</output>

<gadget id="calculator">(35/24) - 1</gadget>
<output>11/24 = around 0.458333</output>

<gadget id="calculator">(1/30) * 2</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(1/40) + (1/15)</gadget>
<output>11/120 = around 0.091667</output>

<gadget id="calculator">(11/24) / (11/120)</gadget>
<output>5</output>

<result>5</result>