For a pile of sand, (2/5) tons are used to repair the wall, (3/10) tons are used to repair the floor, and there is still (1/5) tons left. How many tons is this pile of sand?
一堆沙子，修墙用去了(2/5)吨，补地板用去(3/10)吨，还剩下(1/5)吨，这堆沙子原来多少吨？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(2/5) + (3/10) + (1/5)</gadget>
<output>9/10 = around 0.9</output>

<result>9/10 = around 0.9</result>