Who will use their brains, math brains

Here's my insight, here's how the web turns).

In the middle school context, there is no solution to this problem, which is determined by the nature of odd and even numbers.

Odd (English: odd) mathematical term, colloquially also known as singular, in the integer, the number divisible by 2 is even, the number not divisible by 2 is odd, and the odd single digit is 1, 3, 5, 7, 9. Even numbers can be represented by 2k, odd numbers can be represented by 2k+1, where k is an integer.

Among natural numbers, numbers that are not divisible by 2 are called odd numbers. In everyday life, people usually refer to odd numbers as singular numbers, which are the opposite of even numbers.

There must be an odd number and an even number in two consecutive integers.

The sum of odd numbers and odd numbers is even; The sum of even and odd numbers is odd; The sum of any number of even numbers is an even number. The sum of two numbers with the same parity is even; The sum of two numbers with different parity is an odd number.

The difference between two odd (even) numbers is even; The difference between an even number and an odd number is an odd number.

If a and b are integers, then a+b and a-b have the same parity, i.e., a+b and a-b are both odd or even.

The product of n odd numbers is odd, and the product of n even numbers is even; If one of the cis is even, then the product is even, i.e.: a*b*c*....*Even number*x*y=even, where a, b, c、...x and y are both integers, and the formula can be simplified as: odd number * even number = even number.

The odd number of single digits is ; The single digit of an even number is .

The square of the odd number is divided by the remainder of 1.

The square difference of any two odd numbers is a multiple of .

An odd number is not divisible by 2, it is divided by two and leaves one.

Because the numbers given in this problem are all odd numbers, and the sum of three odd numbers is still an odd number, and it is impossible to get an even number of 30, so there is no solution to this problem.

However, when you get to university, you will have a solution to this problem, and the solution involves derivatives.

Derivative is an important fundamental concept in calculus. When the independent variable x of the function y=f(x) produces an incremental δx at a point x0, the ratio of the incremental δy of the output value of the function to the incremental δx of the independent variable is at the limit a when δx approaches 0 if it exists, a is the derivative at x0 and is denoted as f'(x0) or df dx (x0).

The derivative of any constant is 0, and the sign of the derivative is ', so the three blanks are filled with 15, 15, 15'. 15' = 0, so, 15 + 15 + 15 ' = 30.

I hope I can help you with your doubts.

Don't be misled by the prompt, it just says "the above numbers can be reused" instead of only using the above numbers, if only the above numbers are used (odd + odd + odd = odd) there will be no even numbers, so do you understand?

The above numbers include 2, there is no saying that you can only fill in the numbers in parentheses, 2+15+13=30, I hope it can help you!

Or turn nine upside down to six 6+15+9

It can't be, three odd numbers add up or odd, it can't be even.

No way, it's a **, amusing you.

This trembling friend question should be thought backwards from the end.

If you end up with four locust trees and the opponent leaves, then no matter how many trees he walks, set it to x, you can fill in (4-x) trees accordingly and win. So our goal is to leave four trees at the end and let the other one go.

In the same way, the penultimate step is also a 4 cycle, the other party walks y tree, and you are (4-y) tree.

And so on.

In this way, at the beginning, you go first, go 2 trees; At this time, there are 40 trees left, and then follow the pattern of 4 trees for the two of you to walk in a round. Then, according to the analysis just now, you can change Kai to win.

Hello known 3660

Vertically add the rule.

60 = 36 The left and right sides of the equation are subtracted at the same time.

You can easily get =8

So 10

First of all, write the four spaces as a, b, c, d in order from left to right and top to bottom, and list the four equations according to the meaning of the figure, which can definitely be easily solved by solving the equations, so I don't need to go into details.

If you don't want to solve the equations, you can consider the following ideas for mental arithmetic:

a + b = 8 and b + d is also equal to 8, so a = d;

A + B = 8, A + C = 13, indicating that C is 5 larger than B, and C - D = 6 means that C is 6 larger than D, thus giving that D is 1 smaller than B, and D + B = 8, so D = , B = , C = D + 6 = , A = D =

Hope it helps.

It's simple if you learn to replace it with letters. The four boxes are set to xymn, and they will come out as soon as they are calculated. Whatever the result is, it's out, for example, I'll calculate a:

x+y=8, ②x+m=13, ③y+n=8, ④m-n=6.=8+6=y+m=14, y+m- = y+m-x-y=14-8=m-x=6, m-x)= x+m-m+x=13-6=7, then x=

Others are solved.

Solution: Let the blocks from left to right and top to bottom be x1, x2, x3, x4.

Column equation: x1 ten x2 = 8 (1).

x1 ten x3 = 13 (2).

x3 to x4 = 6 (3).

x2 ten x4 = 8 (4).

Add the above equation to get :

2 (x1 ten x2 ten x3) = 35

x1 ten x2 ten x3 = 35 2 = 17 and 1 2 (5) substitute (1) formula to get:

x3 = 17 and 1 2 a 8 = 9 and 1 2

Substituting x3=9 and 1 2 into (2) get:

x1 = 13 a 9 and 1 2

12 and 2 2 a 9 and 1 2

3 and 1 2 thus obtains: x2 = 4 and 1 2, x4 = 3 and 1 2

My algorithm is different :

After two folds, the rope exceeds the well platform by 9 meters, that is, the remaining 9 2 = 18 meters, after three folds, the rope exceeds the well platform by 2 meters, that is, the remaining 2 3 = 6 meters is less than 18-6 = 12 meters.

So, the well platform is 12 meters deep to the surface of the water.

Rope length: 12 2 + 9 2 = 42 meters.

Solution: Let the depth of the well platform to the water surface be x, and according to the meaning of the question, it can be obtained: (x+9) 2=(x+2) 3 solution: x=12

So the length of the rope is (12+9) 2=42

A: The length of the rope is 42 meters, and the depth from the well platform to the water surface is 12 meters.

The length of the rope is x meters, and the depth of the well platform to the water surface is y meters.

then x 2 = y+

Subtract the two formulas. x/6=7

x=42y=42/2 -9=21-9=12

So the rope is 42 meters long, and the depth from the well platform to the water surface is 12 meters.

Solution: Set the rope length x meters, the well platform to the water surface depth y meters, then:

x÷2－9=y

x÷3－2=y

Solution: x=42, y=12

The well platform to the water surface is x

x+9)*2=(x+2)*3

x=12 rope has (12+9)*2=42

Ma Jian's age is 4 times that of Xiao Min's age, indicating that her mother is 3 times older than Xiao Min.

Mom's mother has always been 32-5=27 years older than Xiaomin, so when Mom's age is 4 times Xiaomin's age, Xiaomin is 27 3=9 years old, and it will take another 9-5=4 years, and Xiaomin will be 9 years old by then.

The last question is whether the finch is old and asks how old Xiaomin will be by then? Because I'm 5 years old this year, I've said it.

Four years later, Xiaomin was 9 years old and her mother was 36 years old.

The mother's age is 4 times that of Xiaomin, indicating that the mother is 3 times older than Xiaomin.

Mom has always been 32-5=27 years older than Xiaomin, with Huai.

Therefore, when the mother's age is 4 times that of Xiaomin's old age, Xiaomin is 27 3 = 9 years old, and it will take another 9-5 = 4 years, and then Jingdong will wait for Xiaomin to be 9 years old.

The number of cubes between 500 and 999 is only 8 3 = 512; 9 3 = 729, and then the sum of the hundred digits and the ten digits equals the single digit, indicating that only 729 satisfies the topic

Find out all the cubic numbers greater than 500 and less than 1000: 512,729.

Only 729 is squared, and the sum of the hundred and ten digits is equal to the single digit.

729 is the cube of 9 and the square of 27.