1, 24 plus 8, () is the divisor of (), and () is the multiple of ().
2. In 1, 2, 3, 9, 24, 4 1 and 5 1, the odd number is (), the even number is (), the composite number is (), () is odd but not prime, and () is even but not.
3. The minimum multiple of a number is 12, and this number has () divisors.
All divisors of 4.2 1 are (), and all prime factors of 2 1 are ().
5. The prime factor of a composite number is all prime numbers within 10, and this composite number is ().
6.A = 2× 2× 5, B = 2× 3× 3, the greatest common divisor of A and B is (), and the least common multiple is ().
7.a and B are prime numbers, their greatest common divisor is (), and their least common multiple is ().
Within 8 and 20, the number that is both even and prime is (), and the number that is odd but not prime is ().
9. The prime factor of the decomposition of 17 1 is ().
Second, the judgment (tick "√" for the right and "×" for the wrong)
1, any natural number has two divisors. ( )
2. There is no common divisor between two prime numbers. ( )
3. All prime numbers are odd numbers. ( )
4. Natural numbers are either odd or even. ( )
5. Because 2 1? = 3, so 2 1 is a multiple and 7 is a divisor. ( )
6. Prime numbers can be odd or even. ( )
7. Because 60 = 3, 3, 4 and 5 are all prime factors of 60. ( )
8, 8 is divisible by 0.4. ( )
9. 18 is both a divisor of 18 and a multiple of 18. ( )
Two numbers with common divisor 1 are called prime numbers. ( )
1 1. Because the common divisor of 8 and 13 is only 1, 8 and 13 are both prime numbers. ( )
12, the common divisor of all even numbers is 2. ( )
Third, choose (put the serial number of the correct answer in brackets)
1, the following groups of numbers, the first number can be divisible by the second number is ().
(1)0.2 and 0.24 (2)35 and 5 (3)5 and 25
2, the following groups, a group that must not be a prime number is ()
(1) prime numbers and composite numbers (2) odd numbers and even numbers
(3) Prime Numbers and Prime Numbers (4) Even Numbers and Even Numbers
3. The prime factor of decomposing 2 10 is ()
( 1)2 10=2×7×3×5× 1
(2)2 10=2×5×2 1 (3)2 10=3×5×2×7
4, the sum of two odd numbers ()
(1) is odd (2) is even (3) may be odd or even.
5. If both A and B are natural numbers, and a÷b=4, then the greatest common divisor of A and B is ().
( 1)4 2 a 3 b
6. A composite number has at least () divisors.
( 1) 1 (2)2 (3)3
7 and 6 are () of 36 and 48.
(1) divisor (2) common divisor (3) greatest common divisor
8, there are four numbers, 4, 5, 7, 8, which can form () groups of prime numbers.
( 1)3 (2)4 (3)5
9. The side length of a square is odd, and the circumference of this square must be ().
(1) prime number (2) odd number (3) even number
10, the number divisible by 3 in the following numbers is ()
( 1)84 (2)8.4 (3)0.6
1 1, the smallest number divisible by 2, 3 and 5 at the same time is ().
( 1) 100 (2) 120 (3)300
12, 8 and 5 are ()
(1) prime number (2) prime number (3) prime factor
13, it is known that A can be divisible by 23, so A is ().
(1)46 (2)23 (3) 1 or 23
14. If a is used to represent natural numbers, then even numbers can be expressed as ().
( 1)a+2(2)2a(3)a- 1(4)2a- 1
15, the smallest number divisible by 9, 12 and 15 is ().
( 1)3 (2)90 (3) 180
Ability and quality improvement
1, the greatest common divisor of numbers A and B is 3, the least common multiple is 30, the known number A is 6, and the number B is ().
2. When a number is divisible by 6, 7 and 8, it is 1, and the minimum number is ().
There are five numbers: 9, 7, 2, 1 and 0. The smallest four digits that can be divisible by 2, 3 and 5 at the same time is ().
4. A bus * * * starts from a bus stop. 1 Road runs every 5 minutes, Road 2 runs every 10 minutes, and Road 3 runs every 12 minutes. After these three cars leave at the same time, how long does it take to leave at the same time?
Infiltration, expansion and innovation
Students from classes 1 and 5 1 go to physical education class, with three rows less 1 person, four rows more than three people, five rows less 1 person, and six rows more than five people. What is the minimum number of people in physical education class?
Xiaohong planted trees around the playground. At first, she planted a tree every 3 meters. After planting 9 trees, she found that there were not enough saplings, so she decided to replant and plant a tree every 4 meters instead. How many trees don't need to be pulled up when replanting at this time?
There is no answer.