In this worksheet, we will practice identifying prime and composite numbers and differentiating between them.
Q2:
Is 21 a prime or a composite number?
- A a composite number
- B a prime number
Q3:
Is 23 a prime or a composite number?
- A a prime number
- B a composite number
Q4:
All prime numbers are odd except .
Q5:
Determine whether the number 85 is prime, composite, or neither.
- Aneither prime nor composite
- Bprime
- Ccomposite
Q6:
Fady is learning about prime numbers. He knows that 5 is a prime number, because the only factors of 5 are 1 and 5.
Is 9 a prime number? Why?
- A No, because 3 is a factor.
- B Yes, because its only factors are 1 and 9.
Q7:
Maged says that 1 is a prime number because it only has 1 factor pair.
Is he correct? Why?
- A No, because all odd numbers are prime.
- B Yes, 1 only has one factor.
- C Yes, because all odd numbers are prime.
- D No, prime numbers have two factors, 1 only has one factor.
- ENo, prime numbers have more than two factors, 1 only has one factor.
Q8:
Mariam says that every even number is composite because 2 is a factor.
Is she correct? Why?
- A Yes, because all odd numbers are prime.
- B Yes, because 2 is an even number.
- C Yes, because 2 is even and composite.
- D No, because 2 is even and prime.
- E No, because 2 is even and composite.
Q12:
A teacher asked her class to colour all the prime numbers between 1 and 10. Here are some of their answers. Which one is correct?
- A
- B
- C
- D
- E
Q13:
Nada bought these four raffle tickets, and one of them was the winning ticket.
- A ticket number 34
- B ticket number 15
- C ticket number 23
- D ticket number 17
- Eticket number 18
Q14:
Which of the following is a prime number?
- A 4
- B 8
- C 45
- D 43
Q15:
Is 96 a prime number?
- Ano
- Byes
Q16:
Are the numbers 2, 47, and 79 prime numbers?
- Ayes
- Bno
Q17:
Which of the following is not a prime number?
- A2
- B23
- C73
- D68
Q18:
Find a prime number between 37 and 46.
Q19:
Look at these numbers.
How many of these numbers are prime?
Which is the largest prime number?
Which is the smallest composite number?
Q20:
State two prime numbers that are greater than 15 and less than 95.
- A45, 61
- B44, 60
- C42, 58
- D43, 59
Q21:
All odd numbers greater than 7 can be expressed as the sum of three prime numbers. Which three prime numbers have a sum of 97?
- A17, 18, 62
- B16, 20, 61
- C18, 19, 60
- D17, 19, 61
Q22:
Find the smallest prime number that is greater than 40.
Q23:
Which of the following integer sequences is not guaranteed to have infinitely many primes?
- A
- B
- C
- D
Q24:
How many prime numbers have integers as their square roots?
Q25:
How many prime numbers are there, and why?
- AWe do not know, because computers are not powerful enough to compute as largely as we need.
- BFinitely many, because once you reach a certain size, every number factors into smaller primes.
- CInfinitely many in theory, as you could theoretically extend the sieve of Eratosthenes indefinitely.
- DInfinitely many, otherwise you could simply take the product of all of them and add one.