What is (1/2) the difference between the largest three-digit number and the largest two-digit number.
最大的三位数与最大的两位数的差的(1/2)是多少．
<gadget id="calculator">999 - 99</gadget>
<output>900</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">900 * (1/2)</gadget>
<output>450</output>

<result>450</result>