There are several tons of grain in each warehouse. After 1 / 3 of the grain is transported from warehouse A to warehouse B, 2 / 7 of the grain is transported from warehouse B to warehouse a There are several tons of grain in each warehouse. After one third of the grain is transported from warehouse A to warehouse B, two seventh of the grain is transported from warehouse B to warehouse A. at this time, the grain stock of warehouse A and warehouse B is equal. How much of the grain in warehouse A is that in warehouse B?

There are several tons of grain in each warehouse. After 1 / 3 of the grain is transported from warehouse A to warehouse B, 2 / 7 of the grain is transported from warehouse B to warehouse a There are several tons of grain in each warehouse. After one third of the grain is transported from warehouse A to warehouse B, two seventh of the grain is transported from warehouse B to warehouse A. at this time, the grain stock of warehouse A and warehouse B is equal. How much of the grain in warehouse A is that in warehouse B?

If the last is all 1, then the second warehouse has 1 / (1-1 / 3) = 3 / 2 before the first warehouse reaches 1 / 3
1-1 / 2 = 1 / 2
Then the original warehouse has (1 / 2) / (1-1 / 3) = 3 / 4
Warehouse B has 3 / 2-1 / 4 = 5 / 4
So the original grain in a warehouse is (3 / 4) / (5 / 4) = 3 / 5 of that in B warehouse
That is to say, the grain in warehouse A is 3 / 5 of that in warehouse B

A quarter * 4 means () six fifths divided by a third means ()
0.3 is the reciprocal of ()

One quarter * 4 means (1) six fifths divided by one third means (3.6)

Fill the nine numbers 0.1-0.9 into the nine palace grid, so that the sum of the three numbers on the horizontal, vertical and diagonal lines is 1.5. How do I do that

0.4 0.9 0.2
0.3 0.5 0.7
0.8 0.1 0.6

The product of three numbers is 512. If the first number and the third number are subtracted by 2 respectively, they will be equal difference series. Find the three numbers

Let three numbers be a, B, C in turn. According to the meaning of the question, ABC = 512 ∵ three numbers form an equal ratio sequence, ∵ B2 = AC, ∵ B3 = 512, B = 8. Let the common ratio of three numbers be t, then a = 8t, C = 8t, the first number and the third number are reduced by 2 respectively, and the latter sequence becomes 8t-2, 8, 8t-2 ∵ the new sequence becomes an equal difference sequence ∵ 16 = 8t-2 + 8t-2

1. A plane can use up to 9 hours of fuel. When it goes downwind, it can fly 1500 kilometers per hour; when it returns upwind, it can fly 1200 kilometers per hour. How many kilometers does the plane have to fly back?
2. Aunt Wang gives a box of biscuits to the children in the big and small classes, with an average of 12 pieces per person. If she only gives them to the children in the small class, they can get 20 pieces per person; if she only gives them to the children in the big class, how many pieces per person?
3. It takes 5 seconds for a train to pass a road sign, 20 seconds to pass a 300 meter cave, and how many seconds to pass an 800 meter bridge
All topics need thinking process and formula, and thinking process must be added!

1、（1500,1200）=6000
6000/1500+6000/1200=9
A: if this plane flies 6000 kilometers at most, it will fly back
2、1/12-1/20=1/30
1/（1/30）=30
A: if you only give it to the children in the big class, you can get 30 yuan each
Set the car length x M
X / 5 = (300 + x) / 20 = vehicle speed
x=100
100 / 5 = 20 seconds
(800 + 100) / 20 = 45 seconds
A: it takes 45 seconds to pass an 800 meter bridge
Formula: (length of vehicle + length of bridge and tunnel) / speed = time

As shown in the figure, in △ ABC, ad ⊥ BC is in D, if BD = ad, FD = CD. (1) verification: ⊥ FBD = ⊥ CAD; (2) verification: be ⊥ AC

The following: (1) to prove: (1) ad 8869; BC, ADC = BDF = 90 ° and \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ac

Fill in the appropriate operation symbol to make the calculation test valid. 8 8 = 1000

There are many solutions, not excluding the similar forms, there are 139 [absolutely no two of them are exactly the same]: (8888-888) / 8 = 1000, (8 + 888) / 8 + 888 = 1000, (888 + 8) / 8 + 888 = 1000 888 + (8 + 888) / 8 = 1000888 + (888 + 8) / 8 = 1000,8 + 8 + 8 + 88 + 888 = 1000,8 + 8 + 8 + 888 + 88 = 1000,8 + 8

If two matrices are equivalent, are their determinants the same

"Equivalence of vector group" and "equivalence of matrix composed of vector group" are two things
They are defined as follows:
Vector group equivalence: two vector groups can be expressed linearly with each other
Matrix equivalence: two matrices have the same form and rank
So it's two things. One can't push the other
Counter example:
(1) The vector group is equivalent, but the matrix is not equivalent. This is simple. As long as the number of vectors in two vector groups is different, the matrix form is different, let alone equivalent
Vector group 1: [1,0] [0,1] [1,1]
Vector group 2: [1,0] [0,1]
In this way, vector groups can express each other, but the matrix formed by vector group 1 is 2 * 3, and the matrix formed by vector group 2 is 2 * 2. The forms are different, and the matrices are not equivalent
(2) The matrix is equivalent but the vector group is not
Matrix 1:
1 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0
Matrix 2:
0 0 0 0
0 0 0 0
0 0 0 0
0 0 0 1
The rank of these two matrices is 1, so they are equivalent, but their column vectors are:
1:[1 0 0 0 ],[0 0 0 0 ],[0 0 0 0 ],[0 0 0 0 ]
2:[0 0 0 0 ],[0 0 0 0 ],[0 0 0 0 ],[0 0 0 1 ]
They can't express each other
You first set my best answer, I Baidu HII teach you

Put the nine numbers 1, 2, 3, 4, 5, 6, 7, 8, 9 in the box to make the equation hold. How many different ways can you think of? □□□=12×□□□=13×□□□

According to the stem analysis, 327 = 12 × 654 = 13 × 981, or 273 = 12 × 546 = 13819

Let n-order matrix a satisfy the equation a ^ 2-2a + I = O, and prove that a ^ 3 = 3a-2i, a ^ 4 = 4a-3i
.RT

Because a ^ 2-2a + e = 0
So a ^ 2 = 2a-e
The equation a ^ 2-2a + e = 0 is left multiplied by A
A^3-2A^2+A=0
So a ^ 3 = 2A ^ 2-A = 2 (2a-e) - a = 3a-2e
So a ^ 4 = 3A ^ 2-2a = 3 (2a-e) - 2A = 4a-3e