Prime and Composite Numbers and a bit of Divisibility Rules

We reviewed a bit of our divisibility rules today in class.  As an intelligent parent mentioned...  Technically all numbers are divisible by all numbers, but they often result in yucky, long decimal values.  When I talk about "divisible" I mean EVENLY divisible.  :)

We completed the large wall Venn Diagram in class today.  A big thanks to my Green class that put ALL of the numbers in the Venn Diagram...

OR THE BOX OF SHAME!



We also began to learn about Prime numbers...

We used the Sieve of Eratosthenes to identify the primes from 1-400.  Try it yourself on this page.

Want some practice learning about Prime and Composite numbers?  Check out this tutorial from Math is fun.

No actual homework this weekend, but we will have a quiz on September 23rd.  I handed out a study guide in class, but it seems like a few people left it behind...  Read below to see what you might have forgotten to bring home!

You are responsible for the following information for this quiz:

1)  Divisibility Rules - you will be given a number and must be able to determine whether it is divisible by 2, 3, 5, or 10 using a Venn Diagram.

          For example:  56,340   

              (You would place the number  in the correct space on the Venn Diagram)

***You must have the divisibility rules memorized***

 

2)  Prime and Composite Numbers - you must know the definitions of prime and composite numbers

          Prime Numbers - the only factors of a prime number are 1 and itself

          Composite Numbers - Composite numbers have other factors besides 1 and itself

You must also be able to sort a list of numbers in two groups: prime & composite

 

3)  Probability & Ratio

You must know how to write a ratio in lowest terms and find the probability of an event as a fraction in lowest terms.

For example ~ Probability:  A junk box contains 5 markers, 6 pom-poms, and 3 beads.  What is the probability of picking a marker from the box without looking?  Answer:  5 out of 14

Ratio:  What is the ratio of pom-poms to markers?  Answer: 6:5 or 6 to 5 or    6

                                                                                                                       5

 

4)  Percent

You must be able to identify the percent when given a fraction or ratio.

=

For example: A junk box contains 10 markers, 6 pom-poms, and 4 beads.  What percent of the pom-poms is in the box?   Answer:  6          30   = 30%

                                                                             20        100

See you all on Monday!  Have a great weekend!

-Miss K  :)