Friday, September 16, 2011

DIVISIBILITY

You have to know the divisibility rules, they can be very helpful when trying to figure out factors especially when you are dealing with numbers that are out of your comfort zone like 482.

Divisibility Rules

A number is divisible by ......
• 2 if the last digit of the number is an even number.
• 3 if the sum of all the digits in the number can be divided evenly by 3.
• 4 if the last 2 digits of the number can be evenly divided by 4.
• 5 if the last digit of the number is a 5 or 0.
• 6 if the the number is divisible by 2 and 3.
• 9 if the sum of the digits is divisible by 9.
• 10 if the last digit of the number is a 0.
CHECK OUT THE DIVISIBILITY RAP. Some of my students last year created this to the theme song of "Fresh Prince of Bel Air." The lyrics are below.

Now this is the story (pause) all about how
divisibility rules gets used in the schools
and we’d like to take a minute just sit right down
We’ll tell you how to divide like the best in town

In Ballard County born and raised
In the classroom where we spend most of our days
Sittin back, list’nin, learnin all cool
Mrs. White teachin divisibility inside the school
She gave a couple problems, they were no good
we started having trouble in her neighborhood
She say 2, 3, 4, 5, 6, 9, 10
Gotta follow the rules if you wanna win

So we listened to the rules and now we believing
You can divide by 2 is the last digits even

Divide by 3? It different you see
The sum of the digits has to divide by 3

The rule for 4 is about the last 2 digits
And if you can divide them by 4 do ya get it?

Dividin by 5 is easy you know
If the number end with 5 or 0

To divdide by 6 you gotta say yes
To 3 and 4 with success

Dividin by 9 is like 3 but this time
You add the digits and divide by 9

And then theres 10 its so easy
When the number ends in 0 it’s a breezy

She gave us some problems bout 12 or 13
And we yelled to the teacher “yo white this aint nothing”
Looked at the homework, we were done quick
Knowin the divisibility rules does the trick