4D Primes, Composite numbers

• Wiskunde
• Middelbare school
• vwo
• Leerjaar 4

Good morning!

Schedule: 

• Learning goals
• What did we do wednesday
• Prime and composite numbers 
• Prime factorization
• Worksheet

Learning goals 

At the end of this lessons I can:

• Define a numbers as a prime or a composite number
• Find the prime factorization of any (whole) number

What did we do last time?

What is HCF(13, 5)?

4D: Primes and composite numbers

HCF(13, 5) = 1 

because 13 and 5 are both Prime numbers 

Factors of 13: 

Factors of 5: 

4D: Primes and composite numbers

A prime number is a natural number with only 2 factors

Ex.  The factors of 7 are 1 and 7

4D: Primes and composite numbers

A prime number is a natural number with only 2 factors

A composite number is a natural number with more than 2 factors

Ex.  The factors of 7 are 1 and 7

Ex.  The factors of 10 are 1, 10, 2, 5

4D: Prime factorization

Every Composite number can be written as the product of prime numbers factors

6 = 2 ⋅ 3

15 = 3 ⋅ 5

4D: Prime factorization

With larger numbers we can use 2 strategies: 

Repeated division

or 

Factor tree

Repeated division

180

Factor tree 

180

Write along!

4D: Prime factorization

Repeated division or Factor tree? 

Use what works best for you!!

Homework

          Worksheet (ask for answer sheet)

4D            2, 6efgh, 7behk, 8

                                      MyiMaths

Finished your homework?

4D: Primes and composite numbers

Step 1: Is 1 a prime number? 

4D: Primes and composite numbers

Step 1: Is 1 a prime number? 

Step 2: Is the next number a prime number? 

Yes            Circle it

No             Cross it off

4D: Primes and composite numbers

Step 1: Is 1 a prime number? 

Step 2: Is the next number a prime number? 

Yes            Circle it

No             Cross it off

Step 3: Cross off any number that is divisible by the number from step 2

4D: Primes and composite numbers

Step 1: Is 1 a prime number? 

Step 2: Is the next number a prime number? 

Yes            Circle it

No             Cross it off

Step 3: Cross off any number that is divisible by the number from step 2

Step 4: Repeat step 2 and 3