There are 4 red balls and 1 yellow ball in an opaque bag. These balls are of the same size and shape. Xiao Ming touches a ball and puts it back into the bag. He touches it 4 times and it is all red balls. He touches it the 5th time. what is the probability of a yellow ball
一个不透明的袋子中装有4个红球和1个黄球，这些球大小、形状相同，小明摸一个球再放回袋中，他摸了4次都是红球，他第5次摸到黄球的可能性是多少
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>