There are 3 red balls and 8 blue balls in a cloth bag, and how many red balls are added to the cloth bag, the probability of touching a red ball at this time is (1/2).
一个布袋里有3个红球，8个蓝球，再往布袋里加多少个红球，这时摸到红球的可能性是(1/2)．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">8 / (1/2)</gadget>
<output>16</output>

<gadget id="calculator">16 - 8 - 3</gadget>
<output>5</output>

<result>5</result>