Put 3 white balls and 7 red balls in a box, let you draw 1 ball out of it at any time, and put it back. If you touch 20 times in this way, the number of times you touch the red ball accounts for approximately the total number of times.
把3个白球和7个红球放在一个盒子里，让你每次从中任意摸出1个球，然后放回．照这样摸20次，摸出红球的次数大约占总次数的多少．
<gadget id="calculator">3 + 7</gadget>
<output>10</output>

<gadget id="calculator">7 / 10</gadget>
<output>7/10 = around 0.7</output>

<result>7/10 = around 0.7</result>