自主练习,（选自教材,P24-P25,）,490,570,230,120,540,300,400,100,90,900,80,800,40,400,80,800,1200,2000,1500,1800,1600,400,960,2100,20 30 600,10 20 200,4090=3600,（棵）,答：一共有,3600,棵树苗。,1+19=20,（人）,3020=600,（元）,答：一共要付,600,元。,450,2000,1200,70,3650,3510=350,（千克）,一共有多少颗树？,