SIMPLE NUMBER SENSE

http://library.thinkquest.org/17888/prn_all.shtml

WHOLE numbers greater than one (1) come in two flavors, composite and prime.
  • What is prime number?

A prime number is a whole number that cannot be divided without a remainder, except by itself and one. A prime number has exactly two factors, 1 and itself.

For example, 13 is a prime number because the only factors of 13 are 1 and 13.
The number 8 is not prime because it has four factors: 1, 2, 4 and 8.

The number 1 is not a prime number because it only has one factor (itself).

  • How many prime numbers are there? Infinite!
  • What are the first five prime numbers? 2,3,5,7,11

15 prime numbers less than 50: http://www.ex.ac.uk/cimt/mepres/book8/bk8i2/bk8_2i1.htm

2,3,5,7,11,13,17,19,23,29,31,37,41,43,47

Fundamental Theorem of Arithmetic

Each composite number can be written as a product of prime numbers.

Factor tree derived from 180; 180 = 18x10 = 2x9x2x5 = 2x2x3x3x5

http://library.thinkquest.org/17888/prn_all.shtml

Composite Numbers

The set of composite numbers are all those which have more than two, positive, whole number factors (besides one and the number itself.) For example, the number four is composite because it also has two as a factor besides one and four. In fact, two (2) is the only even number which is not composite.

A factor is a whole number which divides exactly into a whole number, leaving no remainder.

What’s an ARRAY?http://www.eduplace.com/math/mw/background/5/03/te_5_03_overview.html

  • A collection of data items, all of the same type. An array is a composite number of elements
  • An orderly arrangement.
  • A collection of elements in a two dimensional arrangement where no elements are missing.
  • A set of elements lay out in a line.

An array is one way to show the product of two numbers.

108 can be represented in as many arrays as this number has factors. Those are:

  • 2 x 54 = 108 => This array would be a 2 by 54  units in a graphic grid.

  • 6 X 18 = 108 => This array would be a 6 by 18 units in a graphic grid.

  • 9 X 12 = 108 => This array would be a 9 by 12 units in a graphic grid.

Here is that same array broken apart into two smaller arrays, giving students a visual method of understanding the Distributive Property (see below).

 Activities

  • Find the prime factors of the numbers in the box below
  • Use graph paper to represent the composite numbers as arrays, and tree diagrams to find its prime factors.
  • Find two larger number and find its prime factors!

10, 12, 15, 16, 24, 32, 36, 40, 45, 50, 48, 64, 70, 100

 

Suggested links:

http://www.aaamath.com/B/grade5.htm

 

Send mail to Mrs. Yeates: charo@simplethinking.com

This page updated: Sunday, August 30, 2009