There are already 3 red balls and 2 white balls in the bag, how many blue balls should be put in before you can touch any ball, the probability of touching a blue ball is (1/2).
袋子里已经放着3个红球，2个白球，应放入多少个蓝球，才能任意摸一个球，摸到蓝球的可能性是(1/2)．
<gadget id="calculator">3 + 2</gadget>
<output>5</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 - (1/2)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">5 / (1/2)</gadget>
<output>10</output>

<gadget id="calculator">10 - 5</gadget>
<output>5</output>

<result>5</result>