Miscellaneous

Elementary
GCD
LCM
Definitions

Percents

Ratios

Square Roots

Reverses

Junior High
Cube Roots

Mult By 9 (#1)
Mult By 9 (#2)

Mult By 8

Polynomials

Positive Integral Divisors

Sum Of Positive Integral Divisors

Relatively Prime 

Triangular Numbers

Remainders

Divide By 40

Divide By 25

Divide By 9

High School

Pentagonal Numbers

Hexagonal Numbers

Heptagonal Numbers

Octagonal Numbers

Manipulating Polygonal Numbers

Dividing Factorials #1

Dividing Factorials #2

Solving Triangular Numbers

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Hexagonal Numbers:

A.  A Hexagonal Number is a number that creates a hexagon.  In other words:  1, 6, 15, 28, etc.

B.  The n^th hexagonal number can be found by the following:

n(2n - 1)

C.  In number sense, the question will only ask for the n^th hexagonal number.

Ex [1]  The 8^th hexagonal number is __________.

a.  Using the formula we get: 8 x 15 = 120.

b. The answer is 120.

Ex [2]  The 13^th hexagonal number is __________.

a.  Using the formula we get: 13 x 25 = 325.

b.  The answer is 325.

D.  Here are some ways of manipulating hexagonal numbers:

1.  The difference of successive hexagonal numbers is:

4n - 3, where n is the largest

2.  Adding successive hexagonal numbers gives:

4n² - 6n + 3, where n is the largest

NOTE:  You might see #1 on a test, but I doubt you will ever see #2 on a test.