Jinghua Middle School has 120 teachers. The ratio of old, middle and young teachers is 1:3:4. How many middle-aged teachers are there?
京华中学有教师120人，老、中、青教师的人数比是1：3：4，有中年教师多少人．
<gadget id="calculator">1 + 3 + 4</gadget>
<output>8</output>

<gadget id="calculator">3 / 8</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">120 * (3/8)</gadget>
<output>45</output>

<result>45</result>