Elementary school students application questions, please explain the process in detail, 33 l1

Grasp: The concentration is the sugar content, no matter how much water is added, the amount of sugar remains the same.

1) How many grams of sugar are there?

80 10% = 8 (grams).

2) How many grams of sugar water are added to the water?

8 8% = 100 (grams).

3) How much water is added?

100-80 = 20 (grams).

Sugar = 80 10% = 8 grams.

8% sugar water = 8 8% = 100 grams.

Add water = 100-80 = 20 grams.

Analysis: 1) 80 grams of sugar water, his concentration of 10% means"Sugar + water"A total of 80 grams, of which, sugar is 80 10% = 8 (grams).

2) The problem asks us to add water to make the sugar water into 8% sugar water, and in the process, the amount of sugar does not change, and the amount of sugar remains the same as in the original liquid, which remains at 8 grams.

Conclusion: We get a constant amount, and that is that the sugar has always been 8 grams.

Solution: Suppose: 8% solution can be obtained by adding x grams of water.

80×10%=(80+x)×8%

8=(80+x)×

80+x=8÷

80+x=100

x=100-80

x = 20 (grams).

A: After adding 20 grams of water, you can get an 8% solution.

It's a matter of pursuit.

Lan found that Ji Zhi forgot to bring the crayon box, so he knew that Wei immediately went home at the original speed, and when he arrived home, Fangfang's leading distance was 50*2*2=200 meters.

That is, I caught up with these 200 meters in the next 10 minutes, and I had to walk 200 10 = 20 meters more than Fangfang every minute.

Therefore, Lanlan later 50 + 20 = 70 meters per minute.

Their home and school are 70 * 10 = 700 meters apart.

1. Solution: (1) Set the mixed doubles for x games.

x+2（x+4）+2（x+4+4）=64

Solution: x=8

A: Mixed doubles was played for 8 matches;

2) Mixed doubles: 4 8 = 32 (person-times).

Men's and women's doubles: 4 (8+4) 2=96 (person) Men's and women's singles: 2 (8+4+4) 2=64 (person) 32+96+64=192 (person).

A: A total of 192 people participated in all competitions.

2. Solution: (40 1 2+50 1 2) (50-40)=hour) 40 (km).

Answer: The distance between A and B is 200 kilometers, and the driving time of the car here is hours.

1.Reduce the height of the meter. In fact, it reduces the area around a cuboid by one meter long, one meter wide, and one meter high. So the column formula is: (square meters.)

2.This question is the same as the previous question, a total of 4 equal surfaces are added, first find the area of one surface, 48 4 = 12 square centimeters. Knowing the area of a rectangle and its height, you can find its length, 12 3 = 4 cm.

In this way, we know that the original cube has a ridge length of 4 centimeters.

So the column formula is: 48 4 3 = 4 cm (edge length) 4 * 4 * 6 = 96 square centimeters (surface area).

4*4*4=64 cubic centimeters (volume).

3.In this problem, we first need to figure out how many 50 seconds there are in 2 hours. 2 hours = 120 minutes = 7200 seconds. 7200 50 = 144.

Next, it depends on how many 144 1000 can be divided into equally, 1000 144 = 6 and 9. In this way, it seems that 6 people is not enough, so at least 7 people should be used.

Comprehensive column: 1000 (7200 50) = 7 and 12

4.The first thing to see is how many 80g are in it. 1200/80=15.This illustrates the weight of 15 3-meter-long wires. Then the total length of the wire is 15*3=45 meters.

Comprehensive column formula: 1200 80*3=45 meters.

5.Think of a batch of books as unit 1Five machines can complete 1 12 of the total amount in 1 day

Now it is required to figure out how much a machine can accomplish per day. With 1 12 5 = 1 60Knowing the amount of work done by a machine in one day, you can find the amount of work done by three machines in one day, 1 60 * 3 = 1 20

It is clear that this batch of books will take 1 1 20 = 20 days. It can be completed in 20 days with 3 machines and 12 days with 5 machines, so it will take 20-12=8 days more with 3 machines.

Comprehensive column formula: 1 (1 12 5*3)-12=8 days.

1. (

2.The original side length = 48 3 4 = 4 The original surface area is 4*4*6=96 and the volume = 4*4*4=64

3.One person can fold 7200 for two hours 50 = 144 1000 144 = 125 18 = 6 and 17 So 7 people.

1. (square meters.)

2. If the side length of the square is x, then 3x*4=48, x=4, then the surface area of the cube = 4*4*6=96 square centimeters, and the volume of the cube = 4*4*4=64 cubic centimeters.

2*60*60 50 = people, that is, 7 people 4,

12 3-12 = 8 days.

Square decimeter = 80 square centimeters.

80 5 = 16 (square centimeters) This is the base area or cross-sectional area.

From here, it can be seen that the width and height of the cuboid are both 4 centimeters. (16 = 4 4) 40 4 4 + 80 2 = 640 + 160 = 800 (square centimeters) This is the surface area of the original cuboid.

The cross-section is a square, indicating that there are two of them in length, width and height, which are the same length, and the increased area = 5 * [(width + height) * 2] = square decimeter = 80 square centimeters, so width + height = 8 cm.

Then let's discuss it on a case-by-case basis.

1, width = 5, at this time height = 3, find the corresponding surface area.

2, height = 5, then width = 3, find the corresponding surface area, the same size as the previous 3, width = height = 4, find the corresponding surface area.

If the length is increased by 5 cm, only the side area is increased, and because the cross-section is square, the circumference is, that is, the side length is, so the surface area is.

The above units are decimeters).

The original surface is 2L*L+40*4*L, and after the increase, 2L*L+45*4*L, after subtraction, it is a square meter, and the side length is L=4cm

Therefore, the original surface area is 4*4*2+4*4*40=672

"A's salary for 4 days is 40 yuan more than B's salary for 5 days," if you don't count the 40 yuan, or, in other words: 40 4 = 10 yuan per day.

The rest is: A's 4 days' wages are equal to B's 5 days' wages, A's 1 day's wages are equal to B's 5 4 = days' wages, and A's 10 days are equal to B's days. 1120-10 10 = 1020 (yuan) (10 days for a dry job, 100 yuan for supply).

A's 10 days are equivalent to B's days, plus B's 13 days, total: B's daily wage: 1020 yuan), 13 days:

40 13 = 520 (yuan) comprehensive formula: (1120-10 10) (5 4 10 13) 13 = 520 (yuan).

A's 4-day salary is 40 yuan more than B's 5-day wage

then A's 4*-day salary is 40*RMB more than B's 5*-day wage, and B's daily wage.

$40. B's salary is 40 * 13 = 520 yuan.

Solution: Suppose B's salary for one day is x, which can be obtained according to the topic:

5x+40) 10 4+13x=1120 Solve the equation to obtain:

x=4040 13=520 (yuan).

Answer: B gets a salary of 520 yuan.

A: (2200+390-2200 B: 2200-1200=1000.)

The walk is 4km hours, the car is 42 km hours, the bicycle is 12km hours, assuming that the distance from Bebe's house to Grandma's house is x km and the walking distance is 1 2x km, then according to the relationship prompt, x 12+10 60=x 8+x 45x=140 x=km.

1. Let the cost of commodity A be x, and the cost of commodity B is 2200-x, [120%x+115%(2200-x)] 90%-2200=131[(54

x=1200 (yuan).

Check: [120%.]1200+115%（2200-1200）]×90%-2200=（1440+1150）

2. The 3 means to walk 3 kilometers and then change to the bus.

km, 800-700 = 100 km.

Box tease balance, 30 150 * 100% = 20%.

Yuan. Centimeter 50*50*flat bucket cavity square centimeter.

Mountain do 4 = 105 people, 140-105 = 35 people.

1.800*(1-7 rolling 8)=100 (m)3Yuan.

Centimeter 50*50*square centimeter.

5.If the girl has x, then x+3 4x=140, so x=80, the girl has 80 people.

1 line 7 8 divide 800 by 8 times 7, find the reserve number out of 7 8 to get 700, imitate the first and last use 800-700 = 100 kilometers.

2 Divide 180 into 100 parts, one portion, and finally divide 30 by Lao Dou.