After (3/4) of a pile of sand is used up, there is still 50kg left. How many kg does the pile of sand originally weigh?
一堆沙子用去(3/4)后，还剩50kg，这堆沙子原来有多少kg．
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">1 - (3/4)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">50 / (1/4)</gadget>
<output>200</output>

<result>200</result>