3 red discs account for the whole (3/8), and add 1 more red disc, then how much red discs account for the whole.
3个红圆片占整体的(3/8)，再增加1个红圆片，这时红圆片占整体的多少．
<gadget id="calculator">1 + 3</gadget>
<output>4</output>

<gadget id="calculator">3 / 8</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">3 / (3/8)</gadget>
<output>8</output>

<gadget id="calculator">8 + 1</gadget>
<output>9</output>

<gadget id="calculator">4 / 9</gadget>
<output>4/9 = around 0.444444</output>

<result>4/9 = around 0.444444</result>