There are 20 boys and 20 girls in Class 51 of Liyuan Primary School, and one of them is randomly selected to participate in a speech contest. What is the probability of picking a girl?
梨园小学五1班男生20人，女生20人，从中任意挑选一人参加演讲比赛，挑到女生的可能性是多少．
<gadget id="calculator">20 + 20</gadget>
<output>40</output>

<gadget id="calculator">20 / 40</gadget>
<output>1/2 = around 0.5</output>

<result>1/2 = around 0.5</result>