From 4 boys and 3 girls, choose a boy and a girl to participate in the chorus, how many different ways are there to choose?
从4个男生和3个女生中，任选一个男生和一个女生去参加合唱，有多少种不同的选法．
<gadget id="calculator">4 * 3</gadget>
<output>12</output>

<result>12</result>