There are 4 red balls and 5 white balls in the box, if a ball is randomly drawn from it, what is the probability of drawing a red ball
盒内有4个红球、5个白球，从中任意摸出一个球，摸到红球的可能性是多少
<gadget id="calculator">4 + 5</gadget>
<output>9</output>

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

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