It takes 20 days for a project to be completed by two engineering teams, A and B, and it takes 30 days for A to complete it alone. Now the two teams will cooperate for 4 days, and the rest of the project will be done by B alone. How much more? genius to complete?
一项工程由甲，乙两个工程队合作要20天完成，由甲工程队单独完成要用30天，现在先由两队合作4天，剩下的工程由乙队单独做，还要多少天才能完成？
<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/20) * 4</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/20) - (1/30)</gadget>
<output>1/60 = around 0.016667</output>

<gadget id="calculator">(4/5) / (1/60)</gadget>
<output>48</output>

<result>48</result>