Mom bought a piece of fabric, used it to make a pair of pillowcases (3/7), and used it to make a sofa cover (1/7). How much of this piece of cloth is used in total?
妈妈买来一块布料，做一对枕套用去(3/7)，做沙发罩用去(1/7)．一共用去这块布的几分之几？
<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">(3/7) + (1/7)</gadget>
<output>4/7 = around 0.571429</output>

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