Worksheet: Prime and Composite Numbers
In this worksheet, we will practice deciding whether a number is prime or composite.
Q2:
Is 21 a prime or a composite number?
- Aa prime number
- Ba composite number
Q3:
Is 23 a prime or a composite number?
- Aa composite number
- Ba prime number
Q4:
All prime numbers are odd except .
Q5:
Determine whether the number 85 is prime, composite, or neither.
- Aprime
- Bcomposite
- Cneither prime nor composite
Q6:
Michael 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?
- AYes, because its only factors are 1 and 9.
- BNo, because 3 is a factor.
Q7:
Benjamin says that 1 is a prime number because it only has 1 factor pair.
Is he correct? Why?
- AYes, 1 only has one factor.
- BNo, because all odd numbers are prime.
- CNo, prime numbers have more than two factors, 1 only has one factor.
- DNo, prime numbers have two factors, 1 only has one factor.
- EYes, because all odd numbers are prime.
Q8:
Madison says that every even number is composite because 2 is a factor.
Is she correct? Why?
- AYes, because all odd numbers are prime.
- BYes, because 2 is even and composite.
- CYes, because 2 is an even number.
- DNo, because 2 is even and composite.
- ENo, because 2 is even and prime.
Q12:
A teacher asked her class to color all the prime numbers between 1 and 10. Here are some of their answers. Which one is correct?
- A
- B
- C
- D
- E
Q13:
Isabella bought these four raffle tickets, and one of them was the winning ticket.
The winning number is a prime number between 10 and 20. Which of her tickets won the prize?- Aticket number 34
- Bticket number 23
- Cticket number 18
- Dticket number 15
- Eticket number 17
Q14:
Which of the following is a prime number?
- A43
- B45
- C8
- D4
Q15:
Is 96 a prime number?
- Ayes
- Bno
Q16:
Are the numbers 2, 47, and 79 prime numbers?
- Ano
- Byes
Q17:
Which of the following is not a prime number?
- A23
- B73
- C68
- D2
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.
- A44, 60
- B45, 61
- C43, 59
- D42, 58
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, 19, 61
- B17, 18, 62
- C16, 20, 61
- D18, 19, 60
Q22:
Find the smallest prime number that is greater than 40.
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.
- BInfinitely many in theory, as you could theoretically extend the sieve of Eratosthenes indefinitely.
- CInfinitely many, otherwise you could simply take the product of all of them and add one.
- DFinitely many, because once you reach a certain size, every number factors into smaller primes.