A brief discussion about the concept of primes. Also included are some prime-sense: what are the possible last digit of a prime number? How many primes are in the first hundred natural numbers? etc.

There are more amazing stuffs!

# Numbers

those fun stuff in numbers

### Math for Early Age /Elementary (G5 under), Numbers

# Sample Review Quiz for Grade 3 /4

A sample quiz questions for Grade 3/4.

Topics covered: Numbers of 1,000 – 10,000; Addition with Carry; Place Values; Time and Clock; Pattern Rules in Number Sequence.

Reference Purpose only — do not copy.

### Algebra, Numbers

# A surprising expression for π

This article is about a very neat expression that evaluates to the value of π.

It is amazingly surprising!

### Geometry, Junior Math (Gr 6 - 9), Numbers

# How Many Isosceles Triangles Are in a Pentagon – Pentagram?

.Surely you’ve discovered that the figure below is clipped from a pentagon. Right? Yeh! let us focus within the border drawn with a crayon, that is, within triangle DAB. How many isosceles are there within it? (For the moment, ignore the smaller pentagram A’C’E’B’D’ and all the triangle formed by their intersections.) Let’s count it!…

### Geometry, Math BASICS, Numbers

# Protected: The (3-4-5) Pattern for Pythagorean Triplets

There is no excerpt because this is a protected post.

### Geometry, Math BASICS, Numbers

# π Ideas (1) a Fun Way of Finding the π Value

#### This describes a fun way to find the π value.

It does not use any area calculation. Not even directly apply the Pythagorean Theorem. Basically it uses *the radius* as a *unit* to measure *the circumference* along the circle. But how can you measure a curve using a line segment, without getting into tech difficulties? There’s simple yet smart solutions. Read on, you can find that out!

### Numbers

# Prime numbers

Prime numbers, composite numbers, and prime factorization; these concepts are described and examples given.

### Junior Math (Gr 6 - 9), Numbers

# What’s So Special about Number 8208?

The seemingly trivial, innocent number 8208 actually has something special. It is a member of a niche class of numbers called narcissistic numbers. And it has an interesting property that 8^{4} + 2^{4} + 0^{4} + 8^{4}= 8208.

Why the name narcissistic number? Keep reading, you’ll find out.

### Algebra, Junior Math (Gr 6 - 9), Methods of Learning, Numbers

# A Magic-square Like Puzzle, with Usual and Shortcut Solutions

Once we understood a math problem, and mastered relevant methods, we can find many different ways to solve the problem. That is, there are many shortcuts.

### Algebra, Equations and Inequalities, Junior Math (Gr 6 - 9), Math BASICS, Numbers

# Solve /Find a Number by Algebra

Word problems with numbers are a convenient facility to learn equations.