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Level Five > Number and Algebra

# Prime Numbers

Keywords:
Achievement Objectives:

Achievement Objective: NA5-2: Use prime numbers, common factors and multiples, and powers (including square roots).
AO elaboration and other teaching resources

Specific Learning Outcomes:

Solve problems by finding the prime factors of numbers.

Description of mathematics:

Number Framework Stage 8

Required Resource Materials:
Square tiles or cards.
Activity:

#### Using Materials

Problem: “Gerry builds rectangles out of 6 square tiles. Find all the ways of building rectangles with these tiles.”

“Repeat for 7 tiles.”

Discuss why 7 is called a prime number and 6 is not.

(Answer: There is only one way of building 7 namely 7 tiles in a single row. Whereas  6 can also be built as 2 rows of 3.)

Examples: By building rectangles out of tiles determine which of these numbers are prime and which are not: 5 8 11 9 15 13 16.

#### Understanding Number Properties:

Explain why 2 is the only even prime number.

#### Using Number Properties

Problem: “7 has factors 1 and 7, and 7 is a prime number.  6 has factors 1, 2, 3, and 6, and 6 is not a prime number. Complete this general rule: If we look at all the factors of a number, we know when it is a prime number if..".