Math problems (3) 1、 A and B are 100 meters apart, walking at the speed of 2 meters per second and 3 meters per second respectively. At the same time, a's dog runs to B at the speed of 8 meters per second. The dog runs back to a after meeting B, and runs back to B after meeting a, and then runs back to B after meeting A. this cycle, until a and B meet, how many meters has the dog run? 2、 Law finding calculation 1*2*3+2*4*6+...+100*200*300 ——————————————————=? 2*3*4+4*6*8+...+200*300*400 ("-" is a fractional line) 3、 Fill - 15, - 12, - 9, - 6, - 3,0,3,6,9 in the nine palace Make the sum of three numbers of horizontal, vertical and diagonal equal Please hurry. Speed! Even if only one question!

Math problems (3) 1、 A and B are 100 meters apart, walking at the speed of 2 meters per second and 3 meters per second respectively. At the same time, a's dog runs to B at the speed of 8 meters per second. The dog runs back to a after meeting B, and runs back to B after meeting a, and then runs back to B after meeting A. this cycle, until a and B meet, how many meters has the dog run? 2、 Law finding calculation 1*2*3+2*4*6+...+100*200*300 ——————————————————=? 2*3*4+4*6*8+...+200*300*400 ("-" is a fractional line) 3、 Fill - 15, - 12, - 9, - 6, - 3,0,3,6,9 in the nine palace Make the sum of three numbers of horizontal, vertical and diagonal equal Please hurry. Speed! Even if only one question!

1.100 ÷ (2 + 3) × 8 = 160m meteor shower love, wrong, the dog is repeatedly run, the distance has run many times
2.=（1×2×3）/（2×3×4）=1/4
3.6 -15 0
-9 -3 3
-6 9 -12

Three math problems
It takes six hours for car a to get to place a and four hours for car B to get to place A. now the two cars leave from both places at the same time. As a result, they meet at the place 18 kilometers away from the destination. How many kilometers is the distance between the two places?
Wutong, Wutong and Wutong are three kinds of trees planted in a school. The number of Metasequoia trees is 40%. The number of willows is 1/8, which is equal to 1/4 of the parasol tree. The number of 40 species of Metasequoia is known. How many classes of willow trees and Indus trees are there?
There are two baskets of apples, the number of which is equal. Xiaoming takes out 40% from basket a for the first time, and 30 from the second time. The ratio of the number Xiao Li takes out from basket B to the rest is 3:4 for the first time, and 18 from the second time. In this way, the number of apples taken out from the two baskets is still the same. How many apples are there in the first basket?
No equations

It should be the middle point, not the end point
(18 + 18) / (1 / 4-1 / 6) = 432km
2. Willow: (40 / 40% - 40) / [(1 / 4) / (1 / 4 + 1 / 8)] = 40 trees
Wutong is 0.5 times its 40*0.5=20.
3. (30-18) / (3 / 7-0.4) = 420

If you want to answer the question of profit and loss, you can use the equation. There are apples and pears. The number of pears is 1.25 times that of apples. Put both apples and pears into bags. If each bag contains 8 apples and 9 pears, and there are 8 pears after the apples are loaded, how many are the original apples and pears?

Suppose there are x bags
8x=(9x+8)/1.25
10x=9x+8
x=8
So there are 64 apples and 80 pears

What is the quadrilateral connected by the midpoint of each side of any quadrilateral and why? (to prove)

It's a parallelogram
Two diagonals connecting a quadrilateral
The four sides of the quadrilateral to be proved are parallel to the diagonal respectively
So it's a parallelogram

Let f (x) = LG (1-x) be defined as a and B, then a ∩ B = ()
A、（0,+∞）\x05B、（1,+∞）
C、（0,1）\x05D、（-∞,1）
Why is the range R?

D

Asking for help in maths
Judge the sign of trigonometric function, 27 / 5 π = 2 * 2 π + 7 / 5 π. I just want to ask how to calculate this. 27 / 5 π = 2 * 2 π + 7 / 5 π. I have never learned this process. If I can't convert radian to angle, I won't ask you to teach me. Please be concise. Thank you. And 27 / 5 π is the third quadrant angle How is this calculated? Is it a sign comparison?

2 π in the radian system is equivalent to 360 degrees in the angle
When the degrees of the angles differ by a multiple of 360 degrees, the positions of the end edges of the angles are the same (whole circle difference)
Therefore, in the radian system, when the radian difference is an integral multiple of 2 π, the final edge of the angle is the same
So the difference between 27 π / 5 and 7 π / 5 is 4 π, which is twice of 2 π
The trigonometric value of 27 π / is the same as that of 7 π / 5
In addition, since π to 3 π / 2 (i.e. the terminal edge of the angle from 180 to 270 degrees is in the third quadrant), 7 π / 5 is in this range, which is the third quadrant angle. Because 27 π / 5 and 7 π / 5 have the same terminal edge, it is also the third quadrant angle
In order to judge which quadrant is in and calculate the trigonometric function value, we usually convert the angle to between 0 and 2 π before doing it

A rectangle is 84cm long and 48CM wide. Divide it into square pieces of paper of the same size. The side length of a square piece of paper must be the whole centimeter. How many squares can it be divided into?
For the questioner to understand
If the answer is complete and the expression is clear, 5 rewards can be added

If a rectangle is divided into several small squares of the same size, its side length must be the common divisor of the length and width of the original rectangle
It is easy to know that the greatest common divisor of the length and width of a rectangle is 12, so the original rectangle is divided into the smallest number of small squares with side length of 12, with a total of 84 × 48 (12 × 12) = 28

A barrel of oil weighs 100kg, x kg is used every day. There are 76kg left after 6 days. How to express it by equation? X = how many? Please help me solve this problem

A barrel of oil weighs 100kg, x kg is used every day, and 76kg is left after 6 days,
The equation is (100-6x = 76),
X=（4）

How many numbers must be taken out of 1, 2, 3,..., 100 to ensure that the sum of two numbers is equal to 100?
We need to use formulas, not equations

1+99=100
2+98=100
Did you find the law?
How many pairs can the sum of two numbers from 1 to 100 be equal to 100?
50 can't, 100 can't. There are 98 left, which is 98 △ 2 = 47 pairs
To make sure that the sum of two numbers is 100, that is to say, there must be one from 1 to 49, and there must be one from 51 to 99
If there is one from 1 to 49, to ensure that the sum of the other and his is 100, we must ensure that we can get that number
However, only 51 to 99 numbers can be guaranteed, so at least 48 numbers should be taken out without considering 50 and 100
Because 50 and 100 are useless, you need to take out at least 50 to ensure the meaning of the question. If you don't understand, ask again

Cut out the largest square from a rectangle 8 cm long and 5 cm wide, and the remaining area is ()

Cut out the largest square from a rectangle which is 8cm long and 5cm wide, and the area of the remaining part is (15cm & # 178;)