1. I hope primary schools will participate in tree planting activities and assign tasks to grades 4, 5 and 6 according to the ratio of 2:3:5. As we all know, there are 84 more trees planted in grade six than in grade four. How many trees should be planted for this task in the third grade?

5-2=3

84/3=28 (tree)

28*(2+3+5)=280 (tree)

A: In this task, 280 trees were planted in three grades.

Xiaoming read a story book in three days. On the first day, he read 20 pages, 1 more than the second day and 1 more than the third day. How many pages did he read on the third day?

20*( 1+4/ 1)=25 pages

(25+20)/6=9 (page)

A: I read 9 pages on the third day.

3. There are 54 students in the school physical education group, and the number of students in the literature and art group is less than that in the sports group 1 person, and the number of students in the literature and art group is less than that in the sports group 1 person. How many people are there in the science and technology group?

(I can't answer, I didn't explain the relationship between the science and technology group and other groups)

4. Kindergartens always give 2/5 of the biscuits they buy to the big class and the middle class according to the ratio of 3:2. Given that a large class gets 12kg, how many kilograms of biscuits does the kindergarten teacher buy?

12/3=4 (kg)

4*(3+2)=20 (kg)

A: Kindergarten teachers buy 20 kilograms of biscuits.