A pile of yellow sand weighs 400 tons, and 30% of it has been transported away. How many tons are left?
一堆黄沙重400吨，运走了30%，还剩多少吨？
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 - (3/10)</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">400 * (7/10)</gadget>
<output>280</output>

<result>280</result>