The students collected 16 kg of tree species in the fourth grade, 34 kg in the third grade and 12 kg in the sixth grade. How many kg of tree species were collected in the sixth grade?

The students collected 16 kg of tree species in the fourth grade, 34 kg in the third grade and 12 kg in the sixth grade. How many kg of tree species were collected in the sixth grade?

Third grade: 16 × 34 = 12 (kg), sixth grade: 12 △ 12 = 24 (kg); comprehensive formula: 16 × 34 △ 12 = 24 (kg); answer: sixth grade: 24 kg

Two simple mathematical problems
1: What is the product of the quotient of 11 / 4 divided by the sum of 2 / 3 and 1 / 4 multiplied by 1 / 4?
2: What is the difference between 4 / 5 and 2 / 3 of a number by 2 / 7?
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1：(2/3+1/4)/(1/4)
=(8/12+3/12)/(1/4)
=(11/12)/(1/4)
=11/12
2: Let a number be X
(4/5)x-(2/3)x=2/7
(12/15)x-(10/15)x=2/7
(2/15)x=2/7
x=(2/7)*(15/2)
x=15/7
A: one number is 15 / 7

List the formulas
There are some apples. Give 30% of them to Xiao Zhang, give the remaining 20% less than 2 to Xiao Wang, and then give the rest to Xiao Li. In this way, Xiao Li gets 28 more apples than Xiao Zhang. How many apples are there in all?
2. For a project, it takes 10 days for team a to complete it alone, and 15 days for team B to complete it alone?
3. It's two o'clock in the afternoon. How many minutes later will the hour hand and minute hand coincide?
The third question is not necessary

Let Xiao Li get 28 more apples than Xiao Zhang. How many apples are there in total? Suppose there are x apples in total. (x * 30%) + 28 = x * (1-30%) - (x * (1-30%) * 20% - 2) (x * 0.3) + 28 = x * 0.7 - (x *...)

5. Three wooden sticks of a, B and C are inserted in the water. The sum of the three wooden sticks is 360 cm. Three quarters of a is exposed outside the water, four seventh of B is outside the water, and two fifths of C is outside the water. What is the depth of water?
6. For an alcohol bottle, its body is cylindrical (excluding bottle neck), and its volume part is 24 π cubic centimeter high. When the bottle is placed upright, the liquid level height of alcohol is 6 cm, and when it is placed upside down, the height of the spare part is 2 cm. What is the volume of alcohol in the bottle?
7. In order to save water, a city's water use regulations for users are as follows: if the family population is four or more, the monthly water consumption is less than 15 cubic meters; if the family population is three or less, the monthly water consumption is less than 10 cubic meters, the charge is 0.8 yuan per cubic meter; if the water consumption exceeds the above description, the charge is doubled per cubic meter. If the actual water consumption is 25 cubic meters for five users, how much should the water charge be?
8. There is a column of numbers, arranged according to the law: 1,2,2,3,3,3,4,4,4,5,5,5,5,5,6,6,6,6,6,7 The number 200 is ()
9. All the students in class 63 participated in the singing group of small sports group. Some students participated in two groups at the same time. If the number of students in two groups was one fifth of that in sports group and two ninth of that in singing group, the ratio of the number of students who only participated in sports group to that in singing group in this class was ()

1 / 4 a = 3 / 7 b = 3 / 5 C A: B: C = 36:21:15 360 * 36 / (36 + 21 + 15) = 180 180 * 1 / 4 = 45 (CM) 6. Suppose the base area is a, then 6A + 2A = 24 π, a = 3 π 6 * 3 π = 18 π 7.25 ＞ 15 * 0.8 = 12 (yuan) (25-15) * 0.8 * 2 = 16 (yuan) 12 + 16 = 28 (yuan) 8