After adding 0.5 to a number, divide by 0.5, subtract 0.5, multiply the difference by 0.5, the result is still 0.5, what is this number?
一个数加上0.5后，除以0.5，减去0.5，所得的差再乘以0.5，结果还是0.5，这个数是多少．
<gadget id="calculator">0.5 / 0.5</gadget>
<output>1</output>

<gadget id="calculator">1 + 0.5</gadget>
<output>1.5</output>

<gadget id="calculator">1.5 * 0.5</gadget>
<output>0.75</output>

<gadget id="calculator">0.75 - 0.5</gadget>
<output>0.25</output>

<result>0.25</result>