There were 60 students in the fourth grade who planted trees, and each of them planted 4 trees on average, which happened to be finished. Later, some students were sent. At this time, each person planted 3 trees on average to complete the task. How many students were sent?
四年级有60名同学去栽树，平均每人栽4棵，恰好栽完．随后又派来一部分同学，这时平均每人栽树3棵就可完成任务，又派来几名同学？
<gadget id="calculator">4 / 3</gadget>
<output>4/3 = around 1.333333</output>

<gadget id="calculator">60 * (4/3)</gadget>
<output>80</output>

<gadget id="calculator">80 - 60</gadget>
<output>20</output>

<result>20</result>