A pile of sand weighs 500 tons, 30% of it is removed on the first day, and 1/4 is removed on the second day, how many tons are left?
一堆沙重500吨，第一天运走30%，第二天运走(1/4)，还剩多少吨？
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (3/10) - (1/4)</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">500 * (9/20)</gadget>
<output>225</output>

<result>225</result>