There is a batch of coal stored in the coal storage plant, 25% of the total is shipped out on the first day, and 20% of the remaining coal is shipped out on the second day. At this time, the coal storage plant still has 720 tons of coal left. How many tons?
储煤厂存有一批煤，第一天运出总数的25%，第二天又运出了剩余的煤的20%，这时储煤厂还剩余煤720吨，问储煤厂原来存煤多少吨？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">720 / (4/5)</gadget>
<output>900</output>

<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">900 / (3/4)</gadget>
<output>1_200</output>

<result>1_200</result>