Prime and Composite Numbers in Maths
Grade 7 Maths Questions With Detailed Solutions

What are prime and composite numbers in maths? Grade 7 maths questions are presented along with detailed solutions. Detailed Solutions and explanations are included.

What are prime and composite numbers in maths?

A prime number is a whole number greater than 1 that can only be evenly divided by 1 and itself.
Examples: 2, 3, 5, 7, 11,... are prime numbers. If you try to divide them by numbers other than 1 or themselves, the remainder will not be zero.
A composite number is a whole number greater than 1 that can be evenly divided by 1, itself and other numbers.
Examples: 4, 6, 8,12..are composite numbers because:
42 = 2 , 4 is divisible by 1, itself and 2
62 = 3 , 63 = 2 , 6 is divisible by 1, itself, 2 and 3.
82 = 4 , 84 = 2 , 8 is divisible by 1, itself, 2 and 4.
122 = 6 , 123 = 4 , 124 = 3 , 126 = 2 , 12 is divisible by 1, itself, 2, 3, 4 and 6.

Answer the following Questions on Prime and Composite Numbers.

  1. Which of the following numbers are prime?
    1, 6.3, 11, 14, 13, 21, 23, 4/5, 100, 123 .
  2. Which of the following numbers are composite?
    1, 8.4, 15, 13, 9/2, 24, 33.
  3. List all prime numbers between 30 and 50 inclusive.
  4. List all composite numbers between 100 and 110 inclusive.
  5. Is the sum of two prime numbers always a prime number?
  6. Is the product of two prime numbers also a prime number?
  7. Which is the largest 3 digit prime number?
  8. Which is the smallest 2 digit prime number?
  9. List all the two digit prime numbers that can be made from the digits 1, 3 and 6 (used only once each).
  10. Can you find a prime number whose least significant digit (digit on the right) is 0?
  11. Can you find a prime number whose least significant digit (digit on the right) is 5?
  12. Can you find a prime number such that the sum of all its digits is equal to 12?
  13. Detailed Solutions and explanations are included.

Links and References

Middle School Math (Grades 6, 7, 8, 9) - Free Questions and Problems With Answers
High School Math (Grades 10, 11 and 12) - Free Questions and Problems With Answers
Primary Math (Grades 4 and 5) with Free Questions and Problems With Answers
Home Page