Prime Numbers, Nombres premiers (grade 4) Flashcards
(14 cards)
What is the lowest prime number?
2
Are even numbers prime?
Only 2 is prime.
So when making a list of prime numbers, start with 2, but then don’t bother listing any more even numbers because they are all divisible by 2.
Is 4 prime? What reason?
It is not prime since we can find a factor other than itself or 1. In this case, the factor 2 allows us to prove that 4 is composite.
What are the first 5 prime numbers?
2, 3, 5, 7, 11
9 is not prime because it is divisible by 3.
What is the divisibility by 3 rule?
The sum of the digits must be divisible by three for the original number to be divisible by three.
Which odd numbers are not prime between 2 and 20? Explain why.
9 and 15
9 is divisible by 3.
15 is divisible by 3.
There is no need to find another divisor to prove it is not prime.
What are the prime numbers from 1 to 20?
Quels sont les nombres premiers de 1 à 20 ?
2, 3, 5, 7, 11, 13, 17, 19
What is the divisibility by 5 rule?
Must end in 5 or 0 to be divisible by 5.
What are the prime numbers from 21 to 40?
Quels sont les nombres premiers de 21 à 40 ?
23, 29, 31, 37
Sometimes when determining primes, the composite number s can be found by determining if they are divisible by 7 but not by a lower prime number.
In a few composite numbers, the lowest prime is 7 so we cannot find proof that it is composite with just divisibility by 2, 3, and 5.
What is the lowest composite number that can be constructed that is only divisible by 7, and none of the lower primes than 7?
49 = 7 * 7
What are the prime numbers from 41 to 60?
Quels sont les nombres premiers compris entre 41 et 60 ?
41, 43, 47, 53, 59
What are the three numbers you must memorize to be composite since their lowest prime factor is 7?
Quels sont les trois nombres que vous devez mémoriser pour qu’ils soient composites puisque leur facteur premier le plus faible est 7 ?
49 = 7 * 7
77 = 7 * 11
91 = 7 * 13
Above 100 you would need to figure them out like this for example:
119 = 7 * 17
133 = 7 * 19
161 = 7 * 23
203 = 7 * 29
121 = 11 * 11
143 = 11 * 13
187 = 11 * 17
209 = 11 * 19
169 = 13 * 13
221 = 13 * 17
247 = 13 * 19
289 = 17 * 17
It is tough to prove that a number is prime when they get larger!
49 = 7 * 7
77 = 7 * 11
91 = 7 * 13
Au-delà de 100, vous devrez les calculer comme ceci par exemple :
119 = 7 * 17
133 = 7 * 19
161 = 7 * 23
203 = 7 * 29
121 = 11 * 11
143 = 11 * 13
187 = 11 * 17
209 = 11 * 19
169 = 13 * 13
221 = 13 * 17
247 = 13 * 19
289 = 17 * 17
Il est difficile de prouver qu’un nombre est premier lorsqu’il est plus grand !
What are the prime numbers from 61-80?
Quels sont les nombres premiers compris entre 61 et 80 ?
61, 67, 71, 73, 79
What are the prime numbers from 81-100?
Quels sont les nombres premiers compris entre 81 et 100 ?
83, 89, 97 (McDavid)
91 is NOT prime because it is divisible by 7 and 13.
83, 89, 97 (McDavid)
91 n’est PAS premier car il est divisible par 7 et 13.
