Transcript Composite Numbers

• Identify if numbers are
prime or composite.
• Sort whole numbers
(through 50) into sets
containing only prime or only
composite numbers
All numbers can be
divided by themselves
and by one.
Prime Numbers
Prime numbers can ONLY be divided by
themselves and by one.
13 can ONLY be divided by 13 or by 1.
1 Group of 13
OR
13 Groups of 1
Composite Numbers
can be divided by something else, also.
15 can be divided by 5 or 3, as well as by 15 or 1:
5 groups of 3
3 groups of 5
OR
1 group of 15
15 groups of 1
OR
TIP: The easiest way to find out if a
number is prime or composite is to run
through a list of possible divisors.
Can I divide by 2?
ALL even numbers can be divided by 2.
Can I divide by 3?
Add all the digits together, if the SUM of
the digits can be divided by 3, then the
number itself can be divided by 3.
Can I divide by 5?
ALL numbers ending with 0 or 5, can be
divided by 5.
Which numbers are prime?
20
15
11
3
17
19
8
9
21
25
7
13
Prime Numbers are:
20
15
11
3
17
19
8
9
21
25
7
13
Which are composite
numbers?
32
11
5
10
12
27
23
19
2
6
14
18
Composite numbers are:
32
11
5
10
12
27
23
19
2
6
14
18
• Music will play and numbers will be stated.
• If the number is composite, keep walking.
• If the number is prime, sit down in the closest chair
(start walking again, only when you hear a composite
number again).
• Stand up, push in chair, and get ready to start when
the music begins.
• NO TALKING DURING GAME!!!!
Go around room, start counting (person by person), if your number
is composite say it, if it is prime say BUZZ. Try to keep it going
to 50. Repeat and see if the class can do it faster.