The school bought 200 saplings on Arbor Day, and planted 80 in the sixth grade. The remaining saplings were distributed to the fifth and fourth grades at a ratio of 3:2. How many trees should the fourth grade plant?
植树节学校买来200棵树苗，六年级栽种了80棵，剩下的树苗按3：2分配给五年级和四年级去栽，四年级需要栽种多少棵树？
<gadget id="calculator">200 - 80</gadget>
<output>120</output>

<gadget id="calculator">2 + 3</gadget>
<output>5</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">120 * (2/5)</gadget>
<output>48</output>

<result>48</result>