It is known that the average of nine numbers is 90. After one number is removed, the remaining number averages 100. What is the number removed?
已知九个数的平均数为90，去掉一个数后，余下的数平均为100，去掉的数是多少．
<gadget id="calculator">90 * 9</gadget>
<output>810</output>

<gadget id="calculator">100 * 8</gadget>
<output>800</output>

<gadget id="calculator">810 - 800</gadget>
<output>10</output>

<result>10</result>