A pile of cement weighs 50 tons in total. The first time to transport all (1/3), the second time to go away is the first (3/5), how much of this pile of cement is left.
一堆水泥共重50吨，第一次运走全部的(1/3)，第二次远走的是第一次的(3/5)，还剩下这堆水泥多少．
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

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

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(2/3) * (3/5)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (1/3) - (2/5)</gadget>
<output>4/15 = around 0.266667</output>

<result>4/15 = around 0.266667</result>