# How to Use the Factorial Notation

We have had several discussions about the factorial notation, so I think this introduction is a bit late. However, it is important that you know these basic facts in order to perform calculations and understand better in later discussions.

The factorial of a non-negative integer $n$ is the product of all the positive numbers less than $n$. For example, the

$4! = 4 \times 3 \times 2 \times 1 = 24$.

and

$5! = 5 \times 4 \times 3 \times 2 \times 1 = 120$.

In Introduction to Permutations, we have discussed that there are $n!$ ways to arrange $n$ distinct objects into a sequence. For instance, if we have 3 objects namely A, B, and C, then they can be arranged in $3! = 3 \times 2 \times 1 = 6$ ways. The arrangement are as follows:

$ABC, ACB, BAC, BCA, CAB, CBA$.

We have also learned some reasons why mathematicians chose the definition $0! = 1$. Continue reading

# TED-Ed’s Interactive Periodic Table

TED-Ed has recently created an interactive Periodic Table where you can view videos about every element. This project was a collaboration of TED-Ed and Brady Haran of Numberphile. Once you click the video, you can view experiments as well as explanations from experts and teachers about the element.

This is a must view for students taking Chemistry as well as Chemistry teachers.

The video below explains about Hydrogen.

# Ted Talk: How to escape education’s death valley

If you have watched Changing Education Paradigms or, then, you will surely love another lecture from Sir Ken Robinson.  This TED Talk discusses about the 3 principles crucial to the human mind to flourish and how the current system of education work against them. This talk is a must-watch for all teachers, educators, school administrators and policy makers.

For more talks by Sir Ken Robinson, visit his page on TEDTalk.

# Video: Is mathematics discovered or invented?

If there’s a number of trees in a forest, and there’s no one there to count them, does that number exist? This is the same question as the existence of mathematics. Is mathematics discovered or invented? If human beings do not exist, would mathematics still exist?

Watch the video from TED as Jeff Dekofsky traces the history of this famous classic question and how mathematicians throughout history think about it.

# How to Multiply Using Lines and Dots

One of the great things about mathematics is that sometimes, you find mathematical concepts in places that you don’t expect them to be. There are also concepts or representations that seem not connected to mathematics, but you will realize that it is indeed mathematics.

In the video below, observe how to multiply using lines and their intersections.

Don’t just watch  the video for the sake of entertainment. I encourage you to think about it.

Why does the method work?

Can you think of other concepts that is similar to the intersection of lines?

Is there a similar representation or idea that is also connected to this representation?

In the next post, we will try to answer the questions above, so keep posted.