I was a 5th grader and my teacher assigned a math problem

Solution: Set x 3-pointers, then 9-x two-pointers.

3x+2(9-x)=24

3x +18-2x=24

x = 6 A: Scored 6 three-pointers.

There are x three-pointers and 9-x two-point shots.

3x+2(9-x)=21

3x+18-2x=21

x=3 has 3 three-pointers.

Solution: Set x three-pointers.

3x+2(9-x)=21

3x+18-2x=21

x+18=21

x=3A: Scored 3 three-pointers.

Solution: Set x three-pointers and Y two-pointers.

3x+2y=21

x+y=9 gives x=3

y=6A: Scored 3 three-pointers.

A: Scored 3 three-pointers.

9 3-21) (3-2) = 6 2-pointers.

9-6 = 3 3-pointers.

It can be seen as a problem of chickens and rabbits in the same cage.

x+y=93x+2y=21

Will this solve?

Solving x is the result you want.

x=3y=2

Suppose x three-pointers are scored 9-x two-pointers Column: 3x+2(9-x)=21 Solve this equation and calculate x=3 So 3 three-pointers are scored Two-pointers: 9-3=6

Let's say he scored 2 points and scored 9 points, he should have scored 18 points, but he scored 21 points, so he scored 21-18 = 3 threes.

You can use the enumeration method or assume that 20 sheets are all 10 yuan, 20 times 10 to get 200, 200 minus 175 to get 25, 25 divided by 5 to get 5, 20 minus 5 to get 15, so 5 yuan 5 sheets, 10 yuan 15 sheets.

Let all 10 yuan have 200 yuan When every 10 yuan is exchanged for 5 yuan 200 yuan, he is 10-5 = 5 yuan 200-175 = 25 yuan We know that 25 5 = 5 then 5 yuan has 5 pieces 10 yuan has 20-5 = 15 pieces The full formula is (20*10-175) (10-5)=5 You can also think of all the money as 5 yuan When each piece of 5 yuan is exchanged for 10 yuan, there will be 5 yuan more You can get (175-20*5) 5=15 then there are 15 pieces for 10 yuan and 5 pieces for 5 yuan.

Solution: Let the five-yuan one have x sheets and the ten-yuan one has y sheets, and the equation can be obtained as follows with known conditions: (1) x+y=20

2.） 5x+10y=175

Multiply Eq. (1) by 5 to get Eq. (3) 5x+5y=100, and Eq. (2) minus Eq. (3) gives us 5y=75 y=15, and substituting y=15 into Eq. (1) gives x=5

Solution: If there are x sheets for five yuan, then there are (20-x) sheets for ten yuan.

5x+10(20-x)=175 The number of five yuan multiplied by the number of tens plus the number of ten yuan multiplied is equal to 175 yuan.

5x+200-10x=175

5x+200=175+10x

200=175+5x

5x=25x=5 (five yuan).

20-5 = 15 (sheets) ten yuan.

If $5 has x sheets, then $10 has 20-x sheets.

5*x+(20-x)*10=175

Solution: x=5

If there is x 5 yuan, then 10 yuan has (20-x) 5x + 10 (20-x) = 175

5x+200-10x=175

5x=25x=5, then there are 20-5=15 pieces of 10 yuan.

Set Xiaohua has 5 yuan x sheets, and 10 yuan has y sheets.

x+y=20 (20 shots in total).

5x+10y=175 (add up to 175 yuan) to get x=5

y=15 So Xiaohua has 5 sheets of 5 yuan and 15 sheets of 10 yuan.

10*15+5*5=175

5 yuan and 10 yuan each have 5 and 15 yuan.

The question is wrong, please correct Xiaohua has 20 pieces of five yuan.

110-8=102 (person) 76+50=126(person) 126-102=24 (person), so there are 24 people who book both.

There were 110-8 = 102 people who ordered.

So the intersection of the two books is 76 + 50-102 = 24 people.

110-8 = 102 people subscribed to the publication.

Of these, 102-76 = 26 people only booked fairy tales.

Then 50-26=24 people have booked both.

Composition King x Fairy Tale y Z rule of both kinds.

1、x+y-z=110-8

2、x=76

3、y=50

So z=24

Calculate multiplication and division first, then add and subtract, calculate from left to right, if there are parentheses, then calculate the parentheses first. Please refer to ** for the detailed process.

(2) The number of copies sold by the Forest Daily News.

(3) Each copy of "Story Newspaper" ** (yuan).

There were several bottles of candy, one of which was eaten several (slightly lighter in mass), and the rest were of equal quality. Give me a balance to watch, I can weigh 3 times brother orange will definitely find the bottle with a few less. How many bottles (bottles) might there be for these candies?

These candies may have 10 to 27 bottles.

The circumference of the wheel is 66 cm

Because it is 100 laps, the wheels go 66 m per minute

With distance speed, got.

Answer: It takes about 10 minutes for Xiaofang's car to get from home to school.

66 cm 0 66 m Lu Qing The circumference of the bicycle is 0 66 (m).

2072 (0 hocks 66 100) 10 (minute chain uproar).

66 100 = 6600 cm = 66 meters.

Answer: Xiao Fang's car from the Heng family to the school, the boy needs about 31 points.

I just want to tell you the idea, after reviewing the problem, you can calculate the distance of the wheel by the diameter, that is, the circumference of the circle. Pay attention to unit conversion. Then calculate the distance traveled by a bicycle and multiply it by 100 laps, and then divide the total distance by the speed to get the time. Submission.

The diameter of the bicycle is 66cm=, the circumference = d=, that is to say, the total distance of the manuscript is 2072m, a total of 2072 turns, 1000 laps a minute. So it takes 10 minutes.

400 people divided by 20 groups = 20 people, each group averages 20 people, when finding the maximum and minimum is the maximum + minimum = 20 people * 2 = 40 people, x + y = 40, x is the prime number, y is also a prime number, x is the maximum prime number within forty, y is the smallest prime number thought by 40, and the above conditions are met by x=23, y=17, so x-y=6. Hopefully

To correct the mistake, 400 people are divided into 20 teams, on average, each team is 20 people, you can find that they are all prime numbers, the closest to 20 are 19 and 23, so that 3 teams of 19 people, 1 team of 23 people, exactly 80 people; 15 teams of 19 people, 5 teams of 23 people, together is 400 people, the difference is 4

My answer is 18, which is the maximum 29, the minimum 11, the 10 group 29, and the 10 group 11

20 groups should be made into 400, and as small as possible, only 40 for each of the two groups combined

I understand what you're saying, you look at the rest of the figure as trapezoidal? That's wrong, that's not a trapezoid, it's a trapezoidal plus a rectangle, so, there will be different results.

Method 1: Trapezoidal area + rectangle area = (2+4) 2 2+2 4=14Method 2: Square area Triangle area = 16-2 2 2=14 The answer is the same.

The second algorithm and the first algorithm are not the same at all. According to your title, you yourself are contradictory:

Take the midpoint of the two adjacent sides and draw a diagonal line to get not a trapezoid. So the first method is wrong.

The first method is not correct, take the midpoint of the two adjacent sides and draw a diagonal line, and the rest is not a trapezoid, but a pentagon. is the area of the trapezoid and another triangle.

So.. It's not the same as the second one...

The rest is not a trapezoid! Rather, a pentagon! So you can't use the formula for calculating the trapezoidal area! It can only be calculated by subtracting the area of the triangle from the area of the square!

Solution: 4 4-2 2 2=16-2=14

Note: It should be half of the area of the square 1 4 square area.

Principal and interest: 1000 yuan).

This question is very simple, but it may be a bit of a bonus for you

After-tax interest of 1000 plus the principal of 1000 with it is.

Principal and interest: 1000 yuan).

Trust me (* hee-hee......