project can be completed in 8 hours by A alone, and the work efficiency of B is 4/5 of that of A. How many hours can A and B work together to complete the project?
一项工程，甲独做8小时完成，乙的工效是甲工效的(4/5)，甲乙合做多少小时可以完成这项工程？
<gadget id="calculator">1 / 8</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(1/8) * (4/5)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/8) + (1/10)</gadget>
<output>9/40 = around 0.225</output>

<gadget id="calculator">1 / (9/40)</gadget>
<output>40/9 = around 4.444444</output>

<result>40/9 = around 4.444444</result>