Write the numbers 1, 2, 3, 4 and 5 on the five cards, then mix them and arrange them in a row. The probability that the five digits can be divided by 5 or 2 is () A. 0.8B. 0.6C. 0.4D. 0.2

Write the numbers 1, 2, 3, 4 and 5 on the five cards, then mix them and arrange them in a row. The probability that the five digits can be divided by 5 or 2 is () A. 0.8B. 0.6C. 0.4D. 0.2

The numbers 1, 2, 3, 4 and 5 are written on the five cards respectively. Then they are mixed and arranged in a row. The total number of five digits is A55 = 120. The characteristic of five digits that can be divided by 5 or 2 is that single digits are arranged by 2, 4 and 5. The number of arrangement is C31 × a44 = 72. Therefore, the probability of five digits that can be divided by 5 or 2 is 72120 = 0.6, so B is selected

Write the numbers 1, 2, 3, 4 and 5 on the five cards, then mix them and arrange them in a row. The probability that the five digits can be divided by 5 or 2 is ()
A. 0.8B. 0.6C. 0.4D. 0.2

The numbers 1, 2, 3, 4 and 5 are written on the five cards respectively. Then they are mixed and arranged in a row. The total number of five digits is A55 = 120. The characteristic of five digits that can be divided by 5 or 2 is that single digits are arranged by 2, 4 and 5. The number of arrangement is C31 × a44 = 72. Therefore, the probability of five digits that can be divided by 5 or 2 is 72120 = 0.6, so B is selected

There are two, one and six cards on the table. What number can divide 43?

129 / 43 = 3, because 6 is 9

A four digit number. The sum of this four digit number and its digits is 1999

Let this four digit number be. ABCD. According to the meaning of the title, 1000A + 100b + 10C + D + A + B + C + D = 1999, that is, 1001a + 101b + 11C + 2D = 1999. (1) obviously a = 1, otherwise, 1001a > 2000, we get 101b + 11C + 2D = 998; (2) because the maximum value of 11C + 2D is 99 + 18 = 117, so 101b ≥ 998-117 = 881, there is b = 9, then 11C + 2D = 998-909 = 89; (3) because 0 ≤ 2D ≤ 18. Then 89-18 = 71 ≤ 11C ≤ 89, then C = 7 or C = 8; when C = 7, then 11C + 2D = 7 When C = 8, 11C + 2D = 88 + 2D = 89, d = 12 (rounding off). So this four digit number is 1976

Integral division of numbers
True or false
A number that cannot be divisible by two is odd
A two digit number with a divisor 3 must be a composite number
Because 16 divided by 2 = 8, so 16 is a multiple and 2 is a divisor
15 is divisible by 3
There are four divisors of 28
If the side length of a square is prime, its perimeter must be sum
36, 60, 45, 75, 144, 420, 270, 306, 96, 660, among these numbers, the number that can be divisible by 2,3 is (); the number that can be divisible by 2,5 is (); the number that can be divisible by 3,5 is (); the number that can be divisible by 2,3,5 is ()
When a decimal is expanded 100 times, and then the decimal point is moved one place to the left, the number is 23.5?

A number that cannot be divisible by two is odd
A two digit number with a divisor 3 must be a composite number
Because 16 divided by 2 = 8, so 16 is a multiple and 2 is a divisor
15 is divisible by 3
There are four divisors of 28
If the side length of a square is prime, its perimeter must be sum
Among the numbers 36, 60, 45, 75, 144, 420, 270, 306, 96, 660, the number that can be divisible by 2 and 3 is (36, 601, 444, 420, 270, 306, 96, 660); the number that can be divisible by 2 and 5 is (60420, 270, 660); the number that can be divisible by 3 and 5 is (60, 45, 75, 420, 270, 660); the number that can be divisible by 2, 3, 5 is (60420, 270, 660)
When a decimal is expanded 100 times, and then the decimal point is moved one place to the left, the number is 23.5?
two point three five

1. Fill in the blanks. (26 points) (1) 21 ／ 7 = 3. We say () is a multiple of () and () is

(1) We say (21) is a multiple of (3 or 7) and (3 or 7) is a divisor of 21

Division of primary school numbers
1.1*2*3*…… *Can 36 be divisible by 1001?
2. There are four children whose age is just one year older than each other. The product of their ages is 360. What is the oldest one?
3. 55 students are going to cross the river. It is known that each boat carries an equal number of people, with a minimum of 5 people and a maximum of 12 people?
4. How many primes are there in nine consecutive natural numbers? Why?

1. 1001 = 7 * 11 * 13, these three numbers are between 1-36, so they can be divisible
2. 360 = 3 * 4 * 5 * 6, so the maximum age is 6 years
3. 55 = 11 * 5, 11 is between 5-12, so it's 5 boats, 11 people per boat
4、

Division of elementary numbers
From the 101 numbers of 1.2.3.99.100.101, take any 21 numbers and add them together. There are several different answers

The smallest number is 1 + 2 + 3 + 21=231
The largest number is 81 + 82 + 83 + 84 + 101=1911
There are 231.232.233 from 231 to 1911 There are 1911-231 + 1 = 1681 possibilities

Please explain the division of primary school numbers

Divide the divisor by the divisor and the remainder is zero

1. What is the difference between a three digit number and the sum of its digits, or a three digit number 3 () 5, ()?
2. Four digits 21ab plus 1635 get 38c4. If 38c4 can be divided by 9, find the value of a + B + C
3. Some three digit numbers can be divided by 2, 5 and 11 at the same time. Arrange these three digit numbers from small to large. What's the number in the middle?

Question 1: let three numbers be a, B, C, then 100 * a + 10 * B + c-a-b-c = 99A + 9b = 3 () 5, because 3 () 5 is 3, so a can only take: 3 and 4, but if a is 4, B must be 1, their sum of hundreds exceeds 3, so a = 3, B = 2: 99 * 3 + 9 * 2 = 315