Download Prime and Composite Number - Mendenhall-Jr-PLC

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Parsheena Berch
Resource: JBHM material
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Prime and Composite Number
Bell Ringer:
Page 33 in JBHM binder (DOK 1)
Focus/Introduction:
• Page 104
• Composite Number- a natural number that has
more than two factors.
• Prime Number- a number that has only two
factors, 1 and itself.
• Have you ever heard of a superprime? A
superprime is a number that remains prime
even after digits are removed from the right
side one at a time.
• Example: 2391: remove 1 and 239 is prime,
remove 9 and 23 is prime, remove 3 and 2 is
prime.
Guided Practice: (DOK 1)
•
•
•
•
•
What is a composite number?
(a number having more than two factors)
8 and 4 are examples of composite numbers.
What is a prime number?
(a number that has only two factors, 1 and
itself; 2, 3, 5, and 17 are examples of prime
numbers)
• Is 1 prime or composite?
• It is a lonely number because it is neither
prime nor composite. It is not a prime number
because it does not have exactly two factors,
and it is not composite because it does not
have more than two factors. So, 1 is not prime
or composite.
Divisibility Rules: A number is divisible
by ___ if…
• 2 – The number is an even number, ending in
2, 4, 6, 8, 0.
Example:
• 124: It ends in 4, so it is divisible by 2.
• 124 ÷ 2 = 62
Divisibility Rules: A number is divisible
by ___ if…
• 3 – The sum of the digits is divisible by 3.
Example:
• 150: The sum of the digits, 1 + 5 + 0 = 6, is
divisible by 3, so 150 is divisible by 3.
• 150 ÷ 3 = 50
Divisibility Rules: A number is divisible
by ___ if…
• 4 – The number is even and the last 2 digits
form a number that is divisible by 4.
Example:
• 724: It is even, and the last two digits, 24, is
divisible by 4, so 724 is divisible by 4.
• 724 ÷ 4 = 181
Divisibility Rules: A number is divisible
by ___ if…
• 5 – The number ends in 0 or 5.
Example:
• 105: It ends in 5, so 105 is divisible by 5.
• 105 ÷ 5 = 21
Divisibility Rules: A number is divisible
by ___ if…
• 6– The number is even, and the sum of its
digits is divisible by 3.
Example:
• 450: It is even and the sum of the digits, 4 + 5
+ 0 = 9, is divisible by 3, so 450 is divisible by
6. In other words, if the rule for 2 and the rule
for 3 work, the number is divisible by 6.
• 450 ÷ 6 = 75
Divisibility Rules: A number is divisible
by ___ if…
• 7 and 8 – These rules are too complicated to
actually be shortcuts.
Divisibility Rules: A number is divisible
by ___ if…
• 9 – The sum of the digits is divisible by 9.
Example:
• 450: The sum of the digits, 4 + 5 + 0 = 9, is
divisible by 9, so 450 is divisible by 9.
• 450 ÷ 9 = 50
Divisibility Rules: A number is divisible
by ___ if…
• 10 –The number ends in 0.
Example:
• 1250: It ends in 0, so 1250 is divisible by 10.
• 1250 ÷ 10 = 125
Independent Practice/Activities:
(DOK 2)
•Divisibility Practice:
•Is the first number
divisible by the second?
Explain “why” or “why
not.”
1.
2.
3.
4.
5.
6.
825; 5___
91; 2___
51; 3____
39; 3___
726; 6___
117; 3____
7. 100; 5___
8. 529; 6___
9. 40; 10___
10. 729; 3___
11. 222; 3___
12. 309; 9___
13. 99; 2___
14. 224; 4___
Which of the numbers are prime or
composite? (DOK 1)
1.
2.
3.
4.
5.
6.
7.
8.
825—
17—
91—
25—
51—
1—
39—
29—
Closure:
• Who can explain prime/composite numbers.
• Homework:
List the prime numbers 1—25.