Focus TEKS:
- 3.4F recall facts to multiply up to 10 by 10 with automaticity and recall the corresponding division facts;
- 5.4A identify prime and composite numbers;
- 5.4E describe the meaning of parentheses and brackets in a numeric expression;
- 5.4F simplify numerical expressions that do not involve exponents, including up to two levels of grouping;
Prime and Composite Notes page 1 page 2
Prime Numbers - numbers greater than 1 that have EXACTLY 2 factors, 1 and itself.
Composite Numbers - numbers greater than 1 that have MORE THAN 2 factors.
The numbers we can use to test if a number is Prime are the numbers 2, 3, 5, and 7. Using the rules of divisibility for these numbers, we can tell if any number is a Prime or Composite Number.
Divisibility Rules
- Rule for 2: If the number you are testing is an EVEN number (ends in 0, 2, 4, 6, or 8), then it is divisible by 2. That means it is a COMPOSITE number.
- Rule for 3: Add all the digits together. If the answer you get is divisible by 3, then the number you are testing is divisible by 3. It is a COMPOSITE number.
- Rule for 5: If the number you are testing ends in a 0 or 5, then the number is divisible by 5. It is a COMPOSITE number.
- Rule for 7: Sorry! You just need to know your 7's multiplication facts! If the number you are testing is divisible by 7, then it is a COMPOSITE number.
If your number is NOT divisible by 2, 3, 5, or 7, then it is a PRIME number.
Order of Operations Notes
For 5th grade - No Exponents (that will come in 6th grade)
- Do all GROUPINGS (Parentheses and Brackets) first
- Do all MULTIPLICATION and DIVISION
- Whichever comes first, in order from LEFT to RIGHT
- Do all ADDITION and SUBTRACTION
- Whichever comes first, in order from LEFT to RIGHT