There are four squares (as shown in the figure below) with side lengths of 1m, 2m, 3M and 4m respectively. How much of the area of the white part is that of the shadow part?

White area: (3 × 3-2 × 2) + 1 × 1, = (9-4) + 1, = 5 + 1, = 6 (M2); shadow area: 4 × 4-6 = 16-6 = 10 (M2); 6 △ 10 = 35. Answer: white area is three fifths of shadow area

A and B went to the store with the same amount of money and bought all the notebooks. A took 9 and B took 12. When they got home, B gave a 7.2 yuan. How much is each notebook?

﹙9＋12﹚÷2＝10.5
5) = 4.8 yuan

1. If there is such a four digit number, the corresponding number of each quotient can't be less than 4, then it can't be eaten. So how many four digits can't eat 8743?
2. In 2345 ~ 9986, how many digits are the same as thousand digits?
Please do me a favor, I need it very much!

① 8743 / 4 = 2185.75, that is 1000-2185. There are 2185-1000 + 1 = 1186. ② when the number is 2: 99-35 + 1 = 65, when the number is 3: 99-00 + 1 = 100, when the number is 4: 99-00 + 1 = 100, when the number is 5: 99-00 + 1 = 100, when the number is 6: 99-00 + 1 = 100, when the number is 7: 99-00 + 1 = 100, when the number is 8

Mathematical problems (Mathematical Olympiad)
2+3-4+5+6-7+8+9-10＋.＋98＋99－100=
Write in detail

2+3-4+5+6-7+8+9-10＋.＋98＋99－100= 2+(3-4)+5+(6-7)+8+(9-10)＋.＋98＋(99－100) =2+5+8+...+[3*(n-1)+2]+...+[3*(33-1)+2]-33=2*33-33+3*(1+2+...+n+...+32）=33+3*(1+32)/(32/2)=1617

There are 48 students in the class, 42 of whom have finished mathematics and 37 of whom have finished Chinese,
Additive analysis

42+37-48=31

Mathematical problems sixth grade Mathematical Olympiad
Xiao Ming bought 47 exercise books at the price of 1.40 yuan, 0.6 yuan and 0.4 yuan respectively. He paid 42.40 yuan in total. The 0.6 yuan exercise book he bought was twice as much as the 0.4 yuan exercise book he bought. How many copies of each exercise book did he buy?
Let's talk about the process of solving the equation

If you buy x exercise books for 0.4 yuan, there will be 2x exercise books for 0.6 yuan and 47-3x exercise books for 1.4 yuan
0.4x+0.6*2x+1.4*(47-3x)=42.4
The solution is as follows
x=9
I bought 9 exercise books for 0.4 yuan
There are 18 copies for 0.6 yuan,
47-27 for 1.4 yuan = 20 copies

It is known that the square of 2x + 3x-1 = 0,
Find the value of 3x-1 (2x to the fifth power + 3x to the fourth power + 3x to the third power + 9x to the second power - 5x + 1)

Because 2x & sup2; + 3x-1 = 0
So: 3x-1 = - 2x & sup2;, 1 = 2x & sup2; + 3x, 2x & sup2; = 1-3x, 2x & sup2; + 3x = 1, X ≠ 0
So: (2x ^ 5 + 3x ^ 4 + 3x & sup3; + 9x & sup2; - 5x + 1) / (3x-1)
=（2x^5+3x^4+3x ³+9x²-5x+2x²+3x）/(-2x²)
=（2x^5+3x^4+3x ³+11x²-2x）/(-2x²)
=（2x^4+3x³+3x²+11x-2）/(-2x)
=[x² (2x²+3x) +3 x²+11x-2] /(-2x)
=[4x² +11x-2] /(-2x)
=[2（1-3x）+11x-2] /(-2x)
=5x/(-2x)
=-5/2

On the circular track, when both of them run clockwise, they meet every 12 minutes. If the speed of both of them does not change, one of them runs counter clockwise and meets every 4 minutes. How many minutes does it take for each of them to run a lap?

If the length of this runway is regarded as the whole "1", then the speed of a is: (112 + 14) △ 2 = 16, and the speed of B is: 14-16 = 112; so it takes 1 △ 16 = 6 (minutes) for a to finish a lap, and 1 △ 112 = 12 (minutes) for B to finish a lap. A: for each lap, it takes 6 minutes for the faster one and 12 minutes for the slower one

Mathematics problems in the first year of junior high school
X is a two digit number and Y is a three digit number. Put x on the left side of y to form a five digit number. Then why can this five digit number represent?
It's 1000x + y
Or 100x + y

1000x+y
Suppose x = AB, y = CDE, ABCDE = AB * 1000 + CDE, it looks better

There should be a process
To solve the system of equations to solve the system of equations | X-1 | + | y + 2 | = 3 | X-1 | - 2Y = 4 |
Yes, you're right. It's absolute value
Why is there no answer for 20 times of browsing! This question is really against the sky!

|x-1|+|y+2|=3①
|x-1|-2y=4 ②
① - 2
|y+2|+2y=-1
When y

There are four squares (as shown in the figure below) with side lengths of 1m, 2m, 3M and 4m respectively. How much of the area of the white part is that of the shadow part?