There is a project that A alone needs 10 days to complete, and B alone needs 15 days. After A completes (1/6) of this project first, how many days can A and B cooperate to complete the remaining part? What percentage of the project has A completed?
有一项工程，甲单独完成需要10天，乙单独完成需要15天，甲先完成这项工程的(1/6)后，余下部分由甲乙合作几天可以完成？甲总共完成这项工程的几分之几？
<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/6) + (1/2)</gadget>
<output>2/3 = around 0.666667</output>

<result>2/3 = around 0.666667</result>