Every page of Xiaoming's diary is numbered with 981 numbers from 0 to 9. Please figure out how many pages there are in Xiaoming's diary! Every page of Xiaoming's diary is numbered. He uses 981 numbers from 0 to 9. How many pages does Xiaoming's diary have? There should be a process and answer questions

There are 9 numbers from 1 to 9;
10-99 has 2 * 90 = 180 numbers;
100-199 has 3 * 100 = 300 numbers;
200-299 has 3 * 100 = 300 numbers;
300-359 has 3 * 60 = 180 numbers
At this time, a total of 9 + 180 + 300 + 300 + 180 = 969 numbers are used;
981-969=12,
So we should count four numbers backward, that is 350, 361362363
So Xiao Ming's diary has 363 pages

The mathematics interest group held a test. There were 15 questions in the whole paper. It was stipulated that 8 points would be deducted for each right question and 4 points would be deducted for each wrong question. Xiaoying got 72 points in total, and she did it right______ Question

The wrong questions are: (8 × 15-72) △ 8 + 4, = (120-72) △ 12, = 48 △ 12, = 4 (DAO); he did right: 15-4 = 11 (DAO); a: he did right 11 questions. So the answer is: 11

There are 20 questions in total, 20 points for one right question, 3 points for wrong, 60 points for Xiao Ming, and several right questions for him

Let X be the number of right questions, and the number of wrong questions is 20-x;
The equation is as follows
20*X+（-3）*（20-X）=60
Solve x, that is, the number of right questions

A is a two digit number, B is a three digit number. If a is placed on the left side of B to form a five digit number, then the five digit number is?

It's equivalent to moving a left by 3 bits, multiplying 10 bits by 1000, and the value of B remains unchanged
So this five digit number is 1000A + B
Ha ha, the above two answers are very correct, this question is too easy!

Why are two matrices of the same order equal if they have the same rank?
As the title

The definition of matrix equivalence is:
1. The matrix has the same shape
2. Same rank
No why, that's how it's defined

Is there a column of number 36 12 24 48 item 20?

The latter is twice as much as the former
therefore
The second term is 3 * 2 = 3 * 2 ^ 1 = 3 * 2 ^ (2-1)
The third term is 3 * 2 * 2 = 3 * 2 ^ 2 = 3 * 2 ^ (3-1)
.
Item 20 equals 3 * 2 ^ (20-1) = 3 * 2 ^ 19 = 1572864

Approximate number and significant number of rational number
1 / 3 is approximately equal to? (accurate to 0.1), and the difference between 1 / 3 and its approximate value is? (expressed in fractions, the same below)
1 / 3 is about? (accurate to 0.01), and the difference between 1 / 3 and its approximate value is?
1 / 3 is about? (accurate to 0.001), and the difference between 1 / 3 and its approximate value is?
1 / 3 is about? (accurate to 0.0001), and the difference between 1 / 3 and its approximate value is?
From the above, we can see that the error becomes larger or smaller with the increase of accuracy
A reward of 100 yuan is offered to those who are in a hurry

1 / 3 is approximately equal to (accurate to 0.1, 0.3)? (accurate to 0.01, 0.33), (accurate to 0.001, 0.333), (accurate to 0.0001, 0.3333). From the above, the error becomes smaller with the improvement of accuracy? (fill in the small)
1 / 3-3 / 10 = 1 / 30
1 / 3-33 / 100 = 1 / 300
1 / 3-1 / 1000 333 = 1 / 3000
1 / 3-3333 / 10000 = 1 / 30000

Xiao Hong read a story book. On the first day, she read 45 pages. On the second day, she read one page of the whole book. On the second day, she read 20% fewer pages than on the first day. How many pages are there in this story book?

There is a problem with the title, if you use the equation solution, is 72 pages, but not in line with the meaning of the title

Let m = 2A (A-2), n = (a + 1) (A-3), compare the size

M-N
=2a^2-4a-(a^2-2a-3)
=a^2-2a+3
=(a-1)^2+2
(A-1) ^ 2 ≥ 0, so m > n

The two vehicles a and B are facing each other from a and B at the same time. When they meet, they are 8 kilometers away from the center of a and B. It is known that the speed of vehicle a is 1.2 times that of vehicle B, and the distance between a and B is calculated______ Kilometers

Speed B: 8 × 2 ^ (1.2-1) = 80 (km / h); speed A: 80 × 1.2 = 96 (km / h); meeting time: 8 × 2 ^ (96-80) = 1 (H); distance between ab: (96 + 80) × 1 = 176 (km); answer: the distance between a and B is 176 km