Math Problems Faster ones are a plus!! ）

36 km = 36,000 m 2 hours = 120 minutes 1 hour and a half = 90 minutes.

The distance that A and B walk in one minute: 36000 120 = 300 (m minutes) then the distance traveled in one and a half hours after B departs: 300 * 90 = 27000 (m) then A's speed is:

36000-27000) 40 = 225 (meter minutes) 225 * 60 = 13500 (meter hours) = kilometers per hour).

B's velocity is: 300-225=75 (m-min) 75*60=4500 (m-h) = km-h).

This question is very easy, but there are very few 2-yuan equations used in the sixth grade of primary school, right? I saw it directly, it turned out that it took 2 hours to meet at the same time; Now A has been walking for 2 hours and 10 minutes, and 1 and a half hours after B's departure, the two meet, so it means that A walks for 10 minutes is equal to B walks for 30 minutes. A's speed is three times faster than B's.

It's a lot simpler!

You don't need an equation to get it:

B: 36 (2*3+2)=kmh).

A: km/h).

Of course, binary equations are easier to columnarize.

Let the speed of A x km h and the speed of B y km h.

2（x+y）=36

Simplify: x+y=18

13x/6+

Substituting y=18-x into 13x 6+ calculates.

x=y=

First of all, according to the first condition, we can know that the sum of the speed of the two people is 18 kilometers per hour, and secondly, it can be known from the condition that A walks 40 minutes in advance is equivalent to half an hour walked by A and B (because A and B walk together for one and a half hours), that is, the speed ratio of A and B is 3 to 1, so B's speed is, A's speed is.

The common velocity of A and B is 36 2 = 18 km h

A sets off first, and B sets off for the time they walk together, 18*A walks 36-27=9km

The speed of A 9 2 3 =

B's speed is.

Let the velocity of A be x and the velocity of B y

2（x+y）=36

Simplify: x+y=18

13x/6+

The solution is x= y=

Let A travel x kilometers per hour and B travel y kilometers per hour, then there is 2x*2y=36 (2 3+3 2)x+3 2y=36

The solution is x= y=

Is it okay to set x,y? Let the velocity of A be x and the velocity of B be y.

120x+120y=3600

40+90）x+90y=3600

The solution is x= y=

A 225 meters per minute, and the rest will come out by your own calculation.

Uh, search and see, is there any 6th grade that is so difficult? No way! I was in my first year of junior high school, and I was a representative of the ...... mathematics subjectSpeechless......

1.Original formula = 3x 2y + 3xy + 3x 2-3xy 2-y 2 (simplify first) because the square of (x+3) + ix-y+10i = 0, and the square of (x+3) is greater than or equal to 0, and ix-y+10i is greater than or equal to 0

So the square of (x+3) = 0, ix-y + 10i = 0, so x = -3, y = 7

Bring in the equation to get the original formula = 545

2.(1) A's fee = x*

Cost of B = (x-3)*

2) When x=50 and a=20000, A's cost = 50 * B's cost = 752000

Because B's cost is higher than A's.

So it's better to choose A.

3.Let the *** of this shoe be A, which can be known from the question:

a-60)/60=40%

Therefore, a = 84 yuan, and *** is a 20% discount of the list price, so the list price is 105

A: The list price is 105 and *** is 84

4.Derived from the title.

x-(x-1)/3=-(3x-1)

Solve the equation x=2 11

6.If the number of students is A, then.

The cost of A = 3 * 180+

Cost of B = (a+3)*

1) When A = B.

540+90a=108a+324

a=12 means that when there are 12 students, the two companies charge the same amount.

2) When a=52.

A = 5220

B = 5940

Because A is smaller than B.

Therefore, it is more cost-effective to choose A.

Halo examines the opposite number.

The opposite of 8 is -8

You can also answer directly.

Opposite numbers are not 0 with opposite numbers

So a small 3, then it is -3

The opposite of 8 is -8, and 3 less than -8 is -11

So 8+(-11)=-3

The opposite of 8 is -8A number that is 3 smaller than -8 is -11, so the sum of two numbers = -11 + 8 = -3

1。After traveling a distance of 20 kilometers per hour, the tractor immediately returns to the original low at a speed of 30 kilometers per hour along the same road, so that the average speed of one round trip is (24 kilometers) per hour.

2。On a map with a scale of 1/2500,000, the distance between cities A and B is 16 cm, then on a map with a scale of 1/8,000,000, the distance between cities A and B should be (5 cm).

16 2500000 8000000 = 5 cm.

3。The father said to his son, "I think you were only 4 years old when you were that old, and when you thought I was this old, I would be 79 years old." "My father is 54 years old and my son is 29 years old.

Age difference between father and son: (79-4) 3=25 years.

Now Dad: 79-25=54 years old.

Now son: 54-25=29 years old.

4。China's wildlife resources are very rich, there are 420 species of mammals, accounting for the total number of mammals in the world, and there are about 3750 species of mammals in the world; There are 7,189 species of birds in the world, and there are (1,100) species of birds in China.

5。Use the four numbers 5, 6, 7, and 8 to form two two-digit numbers to maximize their product, and the two two-digit numbers are (85) and (76) respectively; So that their product is the smallest, and the two two-digit numbers are (57) and (68).

Kilometer.

Centimeter. 3. The father is 54 years old and the son is 29 years old.

species, 1100 species.

and 76, 58 and 67

1.24 If the displacement is calculated, it is 0

2. 5cm

3.Is there a mistake in the stem?

(1) 24 (2) 5 (3) children: 29 dad: 54 (4) 3750 It should be the total number of birds in our country, about 1100 species (5) the largest: 86 75, the smallest: 56 87. Pick me.

One: Every time is 1+++300, now it's a matter of how many times to complete: the next time is the sum of every 2 numbers, and the number of the first answer is less than half, the first time there are 300 numbers, the second time to finish 150 numbers, the third time to finish 75 numbers, but at the beginning of the 4th time, the next number will be used, but it does not affect the result, so there are 38 numbers after the 4th time, 19 numbers after the 5th time, 10 numbers for the 6th time, and 5 numbers for the 7th time, There are 3 in the 8th finish, 2 in the 9th finish, and 1 number in the 10th, so the result is (1+300)*300 2*10=451500

2: (root number 3 times a + b) divided by (root number cover liquid 2 times b + a) is a rational number, then, we let this rational number be k, then a and b have a Liang Hui relation, but c does not have any relationship with a and b, I think the question is wrong.