Let me add that prime numbers, that is, prime numbers, are not difficult to learn. The above friend explained clearly, but in the actual exam, you should be able to quickly identify which number is a prime number and calculate which number is a prime number. Only practice makes perfect.

I recommend the memory formula of prime numbers here as follows:

/kloc-prime number ballads within 0/00

"Two, three, five, seven plus eleven.

Thirteen, seventeen

Nineteen, twenty-three, twenty-nine

Thirty-one thirty-seven

4 1, 43, 47

Remember everything firmly.

Fifty three, fifty nine

Sixty-one to sixty-seven

July 1st, July 3rd, July 9th.

83, 89, 97."

Oral judgment of prime number

2357 1 1 (2, 3, 5, 7, 1 1)

Thirteen, seventeen, nineteen, (13, 17, 19)

239, 3 17, (23, 29, 3 1, 37)

539,6 17 (53,59,6 1,67,)

4 139, 7 139 (4 1 43 49 7 1 73 79)

8389, 97 (83 89 97)

/kloc-prime formula within 0/00

Two, three, five, seven, eleven;

13, 19, 17;

23, 29, 37;

Three one, four one, forty seven;

43, 53, 59;

6 1, 7 1, 67;

73, 83, 89;

Add 79, 97;

25 prime numbers cannot be less;

Remember the prime numbers within 100.

Memory method of prime numbers within 100

There are 25 prime numbers within 100. We often use these prime numbers and can remember them in the following two ways.

First, the conventional memory method.

Remember first that the prime product of 2 and 3, 2 and 3 is 6. Prime numbers within 100 are generally around multiples of 6. For example, 5,7, 1 1, 13,19,23,29,31,37,41,43 ... only 25,35. Therefore, the two numbers before and after the multiple of 6 in 100 must be prime numbers as long as they are not multiples of 5 or 7. According to this feature, you can remember the prime numbers within 100.

Second, the classification memory method

We can divide prime numbers within 100 into five types of memory.

The first category: prime numbers within 20, including 8: 2, 3, 5, 7,1,13, 17, 19.

The second category: prime numbers with a unit number of 3 or 9 and a difference of ten digits of 3, totaling 6: 23, 29, 53, 59, 83, 89.

The third category: prime numbers with unit number of 1 or 7 and ten digits difference of 3, totally 4: 3 1, 37,61,67.

The fourth category: prime numbers with unit number of 1, 3 or 7 and ten digits of difference of 3, with a total of five digits: 4 1, 43,47,71,73.

Category 5: There are also 79 and 97 holding numbers.

Prime numbers within 100 and their memory methods

2 3 5 7 1 1 13 17 19 23 29 3 1 37 4 1 43 47 53 59 6 1 67 7 1 73 79 83 89 97

Method:

2 3 5 7 and 1 1

13 17 19 No.21

23 29 3 1 and 37

4143 No.47 5 1

53 59 6 1 and 67

7173 No.79 8 1

83, 89, 97 because it's only 100.

So there is no 10 1.

Prime songs within 100

Skilled memory 100 prime numbers:

Starting with prime number 2357,

2580 plus 39,

3690 plus 7 1,

Talking about friendship,

One, three, seven, nine,

7749911,

Pay attention to irregularities.

Each sentence is explained as follows:

The first sentence and the second sentence: the four one-digit prime numbers, 2, 3, 5 and 7, are the smallest of all prime numbers and can be regarded as the beginning of the prime number team.

The third and fourth sentences: prime numbers with the tenth digits of 2, 5 and 8 are 3 or 9: 23, 29, 53, 59, 83 and 89; Prime numbers with numbers 3, 6 and 9 are 7 or 1: 3 1, 37, 6 1, 67, (9 1,) 97. (Note: 9 1 in brackets is not a prime number. )

The fifth and sixth sentences: prime numbers with 1, 4,7 in the ten digits have four digits: 1 1, 13, 17,19,45438. (Note: 49 and 77 in brackets are not prime numbers. )

The seventh and eighth sentences: 77, 49 and 9 1 are irregular and not prime numbers, so pay special attention to them]

Let the students memorize this jingle in the following ways to get better memory effect:

1. Let the students understand that the three numbers "2580", "3690" and "1470" mentioned in the third, fourth and fifth sentences are all increased by "plus 3".

2. Let students realize that "7749" in the seventh sentence skillfully uses the multiplication formula "7749" and link the two exceptions "77" and "49", which can deepen the accurate memory of these two exceptions.

Note: Arabic numerals are original, and memory methods are in brackets (to be read). For example, 2 (2) means 2 (2) 3 (3) 5 (5) 7 (7)1(1and) 13 (13 and)1. (3) 47 (47) 53 (53) 59 (59) 61(61) 67 (67) 71(71) 73 (73) 79 (79)

Together, it is "two three five seven eleven, thirteen seventeen, nineteen twenty-nine, three one three seven four eleven, four three seven five three five nine six eleven, six three seven three seven nine". 100 and I haven't forgotten the quality list in 838997.

A fast memory method of prime numbers within 100 (1)

I carry the erhu (25) up the mountain to plant trees (prime numbers). I saw the rabbit (2) playing chess (7) with the tiger (5) on the mountain (3). It is raining. The rabbit put on his raincoat (1 1), and the tiger put on his umbrella (13). Together (65438).

At this moment, I suddenly heard a gunshot. It turned out that the second uncle (29) of Anshan (23) was shooting pheasant (37) halfway up the mountain (3 1). He wore pajamas (4 1), held the tiles (43) and cooked the dead chicken (47) for lunch (53). Armed police give medicine to cormorant (67) on the stairs (6 1) (7 1). He was slightly injured (73) and fell while climbing the mountain (83) with the balloon (79). Thanks to Turtledove (89), it was saved (97).

A fast memory method for prime numbers within 100 (2)

(1) Arrange 25 prime numbers within 100 in the following groups and extract 1 bit.

2 3 5 7

1 1 13 17 19

23 29 3 1 37 4 1 43 47

53 59 6 1 67 7 1 73 79

83 89 97

(2) Make an interesting poem with the number of units of 25 prime numbers, and the topic is below.

Anshan weapon (playing forward)

Umbrella balloon (heel)

My uncle went to bite the mountain together,

Three uncles bite the mountain together.

Uncle, go

(3) After memorizing this poem, write the unit number of each prime number in turn by homophonic method. Then fill in ten digits. The rule is that when you see that the last digit is less than the previous digit, add one to the ten digits.