For a rectangular piece of paper, (2/7) is used the first time, and the same amount is used the second time. How much of this paper is used twice?
一张长方形的纸，第一次用去它的(2/7)，第二次用去的与第一次同样多．两次一共用去这张纸的几分之几？
<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">(2/7) + (2/7)</gadget>
<output>4/7 = around 0.571429</output>

<result>4/7 = around 0.571429</result>