If the decimal point of a certain number is moved to the right by one, the number will increase by 31.5. What is the certain number?
某数的小数点向右移动一位，这个数就增加了31.5，某数是多少．
<gadget id="calculator">10 - 1</gadget>
<output>9</output>

<gadget id="calculator">31.5 / 9</gadget>
<output>3.5</output>

<result>3.5</result>