Find the answer to this math problem, find the answer to this math problem

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Untie; According to the inscription, it takes 4+3=7 hours for A to walk a whole journey.

The 4-hour journey of car B is equal to the distance traveled by car A for 3 hours.

Therefore, the time ratio of A and B is 3:4

The velocity ratio of A and B is 4:3

So B is 4-3=1 part from place a.

So each serving is 70 1 = 70 km.

So the whole journey = 70 7 = 490 km.

According to the title, if A completes B's 4-hour journey, then A's 4-hour journey takes B.

When A arrives at place B after walking for hours, it takes hours for B to arrive, and the distance at this time is 50 meters, and B completes the whole process in hours, so the distance between the two places is one kilometer.

Speed and 1 4

Hour conjunction: Remaining: 1-5 8=3 8

Journey: 50 3 8 = 400 3 (km).

The distance of ab is x, the velocity of A is A, and the velocity of B is B;

x (A + B) 4;X A ; x-50) B

A x B = (x-50) so x km.

Let the velocity of A be x and the velocity of B be y, and the place of encounter at four hours is m, then am=4x, bm=4y

4y=Calculate x y separately ab=4(x+y).

Let the distance between the two places be s.

v A+v B)*4=s;

4+A=s;

vB* (4+.) Three-formula simultaneous solvable s=400 3

s = 4 (v A + v B).

s = A. s = B + 50

The combination of the three equations immediately solves s=400 3

It turns out that there are x people in the class.

5/8x+5=（x+5）×16/25

5/8x+5=16/25x+16/5

16/25-5/8）x=5-16/5

3/200x=9/5

x=120120+5=125 people.

Arithmetic methods can also be used.

Think of it this way: it turns out that girls account for 5 8 of the whole grade, and it can be seen that the ratio of girls to boys is 5:3, that is, 15:9, there are 5 more girls, and now it is seen as 16:9, then 16-15 = 1, this part is 5 people, and 25 copies is 5 25 = 125 people.

Title: In**? Specify that the single digit is 4 or 9.

But the number is divisible by 2 and is even, so the single digit is 4

The answer is 13.

Let's see. 46 students, 15 people out of 100. ==》 31 students only had one subject or none of them scored 100 points.

There are 25 students who scored 100 points in language, and 15 students who subtracted 100 points (because 100 points were scored in language) ==> 100 points in 10 language subjects.

There are 23 students who scored 100 points in mathematics, and 15 people who subtracted double percentage points (because they included 100 points in mathematics) ==》8 mathematics single subject 100.

In the end, 31-(10+8)=13 is the person who did not get 100 in both subjects.

13 people. There are 15 students who scored 100 points in both subjects, leaving 46-15 = 31 students. The 31 included those who scored 100 in either subject, and those who scored 100 in one subject in Chinese or mathematics.

The number of people who get a hundred in a certain subject = (25-15) + (23-15) = 18

People who scored 100 points in neither subject = 31-18 = 13

25 + 23-15 = 33 students, which is a student with at least a 100 score in one subject, and 46-33 = 13, which is the number of students who are rest.

There are a total of 46 students, and there are 25 students who score 100 points in Chinese and 23 in mathematics, of which 15 students in mathematics are Chinese and also score 100 points, so those who do not score 100 points are 46-(25+23-15)=13 people.

With 25+23, it means that people who score 100 points in Chinese and 100 points in mathematics are subtracted from the fifteen people who score 100 points in both subjects, and the rest is the person who scores 100 points in at least one subject, 33 people. With 46-33=13, it means that people who don't get 100 in both subjects.

46-25-23+15=13 people; Why +15 because these 15 people are included in the language 100 points, and these 15 people are also included in the 100 points in mathematics. Lost weight, so +15

At the beginning, each person paid for 10 days and returned 1 yuan, so that each person paid 9 yuan, 9 3 = 27 yuan.

Note that only $27 was issued (there is no such thing as $30).

Of the 27 yuan, the boss collected 25 yuan, and the other 2 yuan was collected by the waiter. 25+2 27 yuan.

The nine yuan paid by each person includes two yuan for the waiter, and each person should return 5 3 yuan, but the actual refund of 1 yuan was paid, and 2 3 yuan was paid to the waiter.

3 * 9 = 27 yuan + 2 yuan from the waiter = 29 yuan.

The 27 yuan in this equation includes 25 yuan for the boss + 2 yuan for the waiter, that is, 29 = 25 + 2 + 2, and 2 yuan is added.

In fact, the three of them paid a total of 3*9=27 yuan, the boss 25 yuan, and the waiter 2 yuan.

The average amount of money given to the boss per person is 25 3 = yuan.

If the 1 yuan is not returned, each person will give the boss yuan.

In other words, the money you give to the boss when you calculate it at that time should be calculated in yuan.

Quadrilateral.

Complex ABCD is diamond-shaped.

ab∥cd，ad＝ab＝2

AMN MND

e is the bai point in the ad edge.

ae＝de②

AEM and DUDEN are against the top corners.

aem＝∠den③

by zhi de aem den(

ae＝de，daome＝ne

Quadrilateral amdn is a parallelogram.

If it is a rectangle, then ab dm, so that amd is a right triangle cos dab am ad

cos 60º＝am/2

1/2＝am/2

am＝1

According to the fact that ABCD is a rhombus, dab=60 can verify that AMDN is a parallelogram.

Parallel and equivalent evidence (1).

Cos it according to the angle.

Let the area of the shaded part be s: s=

2a squared) 4

a) a) a

a. 2=squared.

Belch. Can't think of it. Isn't the center of the circle the midpoint of the diameter? =-

The math formula is difficult to type on the computer, but if you look at this problem, you will know that it is done with linear programming. List the equations and constraints, and then draw a diagram to find the optimal solution!!

A is seen as copyax+

by=13cx-y

4 yields baix=3, y=2 substitution into du3a+

2b=13--13c-

2=4, C2B gives 5a-b

13--22 zhi

2 2 formula. 13a=39a

3,b=5a-13=

2 so daoa

3, b = 2, c = 2 to choose d

d，a+b+c=7

The process is as follows: because A misreads the symbol of b and solves x=3, y=2, and substitutes it into the system of equations as:

3a+2b=13

3c-2=4

B misses look. Weight c, solve x=5, y=1, then x=5, y=1 is a set of solutions of the equation ax-by=13, substituting has:

5a-b=13③

According to c=2

Synthesis, solve the binary system of equations about a and b, and solve a=3, b=2 a+b+c=7

$12 (7-3)*.

If x<=3, y=12 yuan.

Otherwise, y=(x-3)*yuan.

A speed B speed 4

A speed: B speed = 5

30 (8-5) (8+5) = 120 km.

There should be a question of how many coins there are to be complete.

Note that pa 2 + pb 2 = pc 2, you should consider using these three sides to form a right triangle and try it with rotation until it reaches seven minutes.