There are some yellow ping-pong balls in a box. In order to estimate the number of balls, we put 20 white ping-pong balls into the box. After mixing thoroughly, we randomly take out 30 balls and find that there are 3 white balls. How many yellow ping pong balls do you estimate were originally in the box?
有一个箱子里放着一些黄色乒乓球，为了估计球的数量，我们把20个白色乒乓球放入箱子中，充分搅拌混合后，任意摸出30个球，发现其中有3个白球．你估计箱子里原来大约有多少个黄色乒乓球？
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">20 / (1/10)</gadget>
<output>200</output>

<gadget id="calculator">200 - 20</gadget>
<output>180</output>

<result>180</result>