Cool Math
Coolmath: Pre Algebra Divisibility Tests
Known as Guzzinta Tests, here are some quick tricks you can learn to see if a number is divisible, can be divided by, another number.
Better Lesson
Better Lesson: Basic Fractions on a Number Line (Divisible by Two)
Third graders create number lines to represent benchmark fractions.
Mathigon
Mathigon: Algebra: Fibonacci Numbers
This lesson focuses on Fibonacci numbers, a pattern based on the sum of the two previous numbers. It offers examples and practice exercises using some form of Fibonacci numbers.