The school assigns the task of planting 171 trees to the sixth grade, fifth grade and fourth grade respectively according to the ratio of 4:3:2. How many trees should the fifth grade divide.
学校把171棵树的植树任务按4：3：2的比分给六年级、五年级和四年级分别去完成，五年级应分多少棵．
<gadget id="calculator">4 + 3 + 2</gadget>
<output>9</output>

<gadget id="calculator">3 / 9</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">171 * (1/3)</gadget>
<output>57</output>

<result>57</result>