There are 3 red balls and 1 yellow ball in a pocket (each time you touch a ball and put it back into the bag), Xiao Ming touches it three times and all he touches are red balls, so the possibility of getting a yellow ball the fourth time how many
一个口袋中装有红球3个、黄球1个(每次摸一个球再放回袋中)，小明摸了三次摸到的都是红球，那么第四次摸到黄球的可能性是多少
<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>