Prime & Composite | Save the Animals
Teach the divisibility rules first
Teaching students the divisibility rules can save a lot of time! Teach the rules and then dedicate one day for practice. This not only helps the students learn the divisibility rules but gives them more practice with division!
Simple – No Prep – Activity:
1) Students will write a 2-digit or 3-digit number of their choice on an index card
2) Pair students up and they will work together to go through each of the divisibility rules
3) After each card they finish, they will write their number and all the numbers the number is divisible by on the board
4) They will grab another card, roll dice to come up with their new number, and go again!
*Challenge students to not use numbers that are already written on the board*
*See how many numbers the whole class can collectively go through!*
Example Conversation Stem:
“Our number is ….”
“Is the last digit an even number?”
– “Yes – the number is divisible by 2” // “No – the n umber is not divisible by 2”
“Is the last digit a 0 or 5?”
– “Yes – the number is divisible by 5” // “No – the number is not divisible by 5”
…so on and so forth…..
Teach what a “factor” is
Discovery learning with some visual aids
1) Explain how the word factor has the word “FACTORY” and a factory produces a “PRODUCT”: factors are the numbers that you multiply to get a product (tie it back to what they know about multiplication and multiplication vocabulary)
2) Whole Class Factor Chains
Product 1: There are no factors – it is special
Product 2: What are it’s factors? 1 and 2 (1×2=2)
Product 3: What are it’s factors? 1 and 3 (1×3 =3)
Product 4: What are it’s factors? 1 and 4 // 2 and 2
Product 5: What are it’s factors? 1 and 5
Product 6: What are it’s factors? 1 and 6 // 2 and 3
…… and so on and so forth ….
Use the factor chains to tie into PRIME and COMPOSITE numbers
1) What do you notice about the lengths of the factor chains?
2) Why do you think some products have more factors than others?
Go into the definition of what a prime and composite number is!
Prime Numbers: It is a number that has exactly two factors (1 and the number itself)
Composite Numbers: It is a number that is a factor of two or more numbers
**1 is not a prime or composite number
3) Identify the prime and composite numbers with the factor chains!
4) Give students time to practice identifying prime and composite numbers with a simple Finding the Prime Numbers Activity and then afterwards, allow students to glue this page into their math journal for their reference.
5) Follow up with this simple dice roll game.
Put divisibility rules + prime and composite together
I find that using a T-Chart is the easiest when teaching finding factors. Connect this back to your patterns unit!
After students have had practice ample practice, put everything together in a fun activity!
Save the animals activity
1) Cut up number cards and tape them onto balloons, beanie babies,
balls, blocks, or whatever item you want students to have sorted
2) Hide items around the room
3) Have designated places in the room labeled as “prime” or “composite”
Have hula hoops set up, circles set up, certain areas set up, etc labeled as prime or composite
4) Have a timer set up for 20-25 minutes
How to play
1) Pair students up // give each pair a recording sheet and a sentence stem
2) Students will walk with their partner to find a hidden item
3) Once they have found a hidden item, they will take it back to their work space
4) They will go through each divisibility rule, find the factor pairs, and determine whether the number is prime or composite
5) They will use the conversation stems and discuss why the number was a prime or composite number
6) Students will record their work on their answer recording sheet
7) Students will walk together to sort the item as prime or composite in the correct designated area