Move the decimal point of a number three places to the left and two places to the right to get 40.9. What is the original number?
一个数的小数点向左移三位，再向右移两位，得到40.9，原数是多少．
<gadget id="calculator">40.9 / 100</gadget>
<output>0.409</output>

<gadget id="calculator">0.409 * 1_000</gadget>
<output>409</output>

<result>409</result>