Arithmetic pages:
Learn how to calculate fast
Multiply with 11 fast [1]
The square of a number that ends in 5 [2]
Irrational numbers
A Proof that the Square Root of 2 is Irational [3]
Special numbers in Arithmetic
142857 [4]
Fibonacci number [5]
Divisibility tests
Test if a number is divisible by 3 [6]
Test if a number is divisible by 6 [7]
Test if a number is divisible by 9 [8]
Test if a number is divisible by a power of 2 [9]
Prime numbers
The definition of prime numbers [10]
There are an infinite number of prime numbers [11]
Calculate sums
The sum of the first n natural numbers [12]
The sum of the first n odd natural numbers [13]
The sum of the squares of the first n natural numbers [14]
The sum of the squares of the first n odd natural numbers [15]
The sum of the cubes of the first n natural numbers [16]
Links:
[1] http://www.9math.com/book/multiply-11-fast
[2] http://www.9math.com/book/square-number-ends-5
[3] http://www.9math.com/book/proof-square-root-2-irational
[4] http://www.9math.com/book/142857
[5] http://www.9math.com/book/fibonacci-number
[6] http://www.9math.com/book/test-if-number-divisible-3
[7] http://www.9math.com/book/test-if-number-divisible-6
[8] http://www.9math.com/book/test-if-number-divisible-9
[9] http://www.9math.com/book/test-if-number-divisible-power-2
[10] http://www.9math.com/book/definition-prime-numbers
[11] http://www.9math.com/book/there-are-infinite-number-prime-numbers-0
[12] http://www.9math.com/book/sum-first-n-natural-numbers
[13] http://www.9math.com/book/sum-first-n-odd-natural-numbers
[14] http://www.9math.com/book/sum-squares-first-n-natural-numbers
[15] http://www.9math.com/book/sum-squares-first-n-odd-natural-numbers
[16] http://www.9math.com/book/sum-cubes-first-n-natural-numbers
[17] http://www.9math.com/book/142857
[18] http://www.9math.com/book/proof-square-root-2-irational
[19] http://www.9math.com/book/fibonacci-number
[20] http://www.9math.com/book/multiply-11-fast
[21] http://www.9math.com/book/product-sum-difference-application
[22] http://www.9math.com/book/test-if-number-divisible-3
[23] http://www.9math.com/book/test-if-number-divisible-6
[24] http://www.9math.com/book/test-if-number-divisible-9
[25] http://www.9math.com/book/test-if-number-divisible-power-2
[26] http://www.9math.com/book/definition-prime-numbers
[27] http://www.9math.com/book/square-number-ends-5
[28] http://www.9math.com/book/sum-cubes-first-n-natural-numbers
[29] http://www.9math.com/book/sum-first-n-natural-numbers
[30] http://www.9math.com/book/sum-first-n-odd-natural-numbers
[31] http://www.9math.com/book/sum-squares-first-n-natural-numbers
[32] http://www.9math.com/book/sum-squares-first-n-odd-natural-numbers
[33] http://www.9math.com/book/there-are-infinite-number-prime-numbers-0
[34] http://www.9math.com/book/142857