After increasing 0.5 by how much, the number obtained is twice it.
把0.5增加多少后，所得的数是它的2倍．
<gadget id="calculator">0.5 * 2</gadget>
<output>1</output>

<gadget id="calculator">1 - 0.5</gadget>
<output>0.5</output>

<result>0.5</result>