There are five numbers whose average is 9. If one of the numbers is changed to 1, then the average of these five numbers is 8. What should be the changed number?
有五个数平均数为9，若把其中一个数改成1，那么这五个数的平均数为8，这个改动的数原来应该是多少．
<gadget id="calculator">9 * 5</gadget>
<output>45</output>

<gadget id="calculator">8 * 5</gadget>
<output>40</output>

<gadget id="calculator">45 - 40</gadget>
<output>5</output>

<gadget id="calculator">5 + 1</gadget>
<output>6</output>

<result>6</result>