1. The following is the number of each class in Grade 5 of Yucai primary school: Class 1: 39, class 2: 41, class 3: 40, class 4: 43, class 5: 12 Which classes can be equally divided into groups with the same number? Which classes can't? Why? 2. Fill in the blanks with prime numbers, which cannot be repeated: 18 = + = + = ++ 3. The difference between the minimum multiple of a number and its maximum factor is () 4. The quotient of the minimum multiple of a number divided by its maximum factor is () 5. If a natural number is smaller than 20, it is a multiple of 2 and has a factor of 7. This natural number is (). There are () factors for the difference of (); there are () factors for the product of a * B There are 42 students in class five

1. The following is the number of each class in Grade 5 of Yucai primary school: Class 1: 39, class 2: 41, class 3: 40, class 4: 43, class 5: 12 Which classes can be equally divided into groups with the same number? Which classes can't? Why? 2. Fill in the blanks with prime numbers, which cannot be repeated: 18 = + = + = ++ 3. The difference between the minimum multiple of a number and its maximum factor is () 4. The quotient of the minimum multiple of a number divided by its maximum factor is () 5. If a natural number is smaller than 20, it is a multiple of 2 and has a factor of 7. This natural number is (). There are () factors for the difference of (); there are () factors for the product of a * B There are 42 students in class five

A: Class 3 and class 5 are OK, because 40 and 42 are combined, and there are three factors. Class 1, class 2 and class 4 are not OK, because 39 and 43 are prime numbers, which cannot be divided into 1 and other numbers. 2.18 = & nbsp; & nbsp; 13 + & nbsp; 5 & nbsp; = & nbsp; & nbsp; & nbsp; 7 + 11 & nbsp; 3

There are three classes in grade one. There are 40 students in class one, 41 students in class two and 39 students in class three
How much do the three classes get?

40 + 41 + 39 = 120 (person) 600 / 120 = 5 (piece) [average person gets 5 pieces]
[class one] 40 * 5 = 200 (pieces)
[class 2] 41 * 5 = 205 blocks
[class 3] 39 * 5 = 195 (pieces)
A: 200 yuan for class one, 205 yuan for class two and 195 yuan for class three
Don't worry about the value of wealth,

For the same volume of alcohol and water, what is the mass ratio____

Mass ratio = density ratio, so it's 0.8:1 = 4:5

The volume ratio of alcohol to water of equal mass is______ The mass ratio of water to alcohol of equal volume is______ (ρ alcohol = 0.8 × 103 & nbsp; kg / m3,)

The density of alcohol is 0.8 × 103kg / m3, and the density of water is 1 × 103kg / m3; (1) since the mass of alcohol and water is equal, let the mass of alcohol and water be m, then according to the density formula ρ = MV, we can get: v = m ρ, so: V wine: V water = m wine ρ wine: m water ρ water = M4: M5 = 5:4; (2) if the volume of water and alcohol is equal, let their volume be V, then according to the density formula ρ = MV, So: m water: m wine = ρ water × V water: ρ wine × V wine = 5V: 4V = 5:4; so the answer is: 5:4; 5:4

Volume ratio of equal mass of alcohol to water? And mass ratio of equal volume of water to alcohol
The volume ratio of alcohol to water with equal mass? The mass ratio of water to alcohol with equal volume?

In a cylindrical measuring barrel, because G is a constant, we remove it, and the remaining ρ and H are just inversely proportional (density is inversely proportional to volume, and volume is directly proportional to height), so the pressure of water and alcohol with the same mass is equal

How many grams of oxygen are contained in 19.6 grams of sulfuric acid? How many grams of hydrogen are contained in 6 grams of sulfuric acid? How many grams of hydrogen are contained in 4.9 grams of sulfuric acid and in water
The elements are the same

There are 19.6 * 64 / 98 g oxygen elements in 19.6 g sulfuric acid
6 * 2 / 98 g sulfuric acid contains 6 g hydrogen element
The hydrogen content in 4.9 g sulfuric acid is equal to that in 4.9 * 18 / 98 g water

The mass of hydrogen in 18G water is equal to the mass of hydrogen in many g sulfuric acid

nH=18÷(2+16)×2=2mol;
M sulfuric acid = 2 △ 2 × (2 + 32 + 64) = 98g;
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Is the mass of hydrogen in 196 grams of sulfuric acid equal to the mass of oxygen in how many grams of water?
The clearer the better

He made a mistake in calculation
196 * 2 / 98 = x * 2 / 18, x = 4.5g water

Is the mass of hydrogen contained in 196 grams of sulfuric acid equal to the mass of hydrogen contained in how many grams of water?
The clearer the process, the better

The mass of hydrogen contained in 196g sulfuric acid is 196 * 2 * 98 = 4G
The mass fraction of O in water is 2 / 18 * 100% = 11.11%
m=4/0.1111=36g

How many grams of water and 49 grams of sulfuric acid (H2SO4) contain the same mass of hydrogen?
How many grams of water and 49 grams of sulfuric acid (H2SO4) contain the same mass of hydrogen

The mass of hydrogen in the two substances is as follows
…………………… H2O………… H2SO4
Hydrogen mass / molecular weight 2/18………… 2/98
Because the material ratio is ?………… 1/49
So the mass of water is: 18 * 49 / 98 = 9g