There are 10 tons of coal in the coal warehouse. After 10% is used, the remaining 10% is transported in. How many tons of coal are there in the coal warehouse at this time?
煤仓库有10吨煤，用去10%后，又运进剩下的10%，这时煤仓库有煤多少吨．
<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 - (1/10)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">1 + (1/10)</gadget>
<output>11/10 = around 1.1</output>

<gadget id="calculator">10 * (9/10) * (11/10)</gadget>
<output>99/10 = around 9.9</output>

<result>99/10 = around 9.9</result>