Pascal's Triangle and Square Numbers

Below are the first few rows of Pascal's triangle:

1 1

1 2 1

1 3 3 1

1 4 6 4 1

1 5 10 10 5 1

1 6 15 21 15 6 1

The numbers in bold are the third diagonal in when Pascal's triangle is drawn centrally. These are the triangle numbers, made from the sums of consecutive whole numbers (e.g. 15 = 1 + 2 + 3 + 4 + 5), and from these we can form the square numbers. All we have to do is add up consecutive numbers from these and we get the square numbers. To get the first square number, we have to add a 0 on to the front of the list:

0, 1, 3, 6, 10, 15, 21...

0 + 1 = 1 = 1^2

1 + 3 = 4 = 2^2

3+ 6 = 9 = 3^2

6 +10 = 16 = 4^2

10 +15 = 25 = 5^2

15 +21 = 36 = 6^2

Incidentally, you can also get the square numbers by taking the differences of numbers two places apart on the 4th diagonal in of Pascal's triangle. The fourth diagonal goes 1, 4, 10, 20 35... , and the differences you get are 1-0 = 1, 4-0 = 4, 10-1 = 9, 20-4 = 16, 35-10 = 25 and so on.

To understand why you get the square numbers from adding together consecutive triangle numbers, you can use a variety of methods. Firstly, if you know that the formula for the nth triangle number is (n^2 + n)/2, then the previous triangle number is n less than this, as it's the same sum of numbers but with (n-1) and not n as the last number you add. If we then add together these two numbers, we get

(n^2 + n)/2 + (n^2 + n)/2 - n

= (1/2)n^2 + n/2 + (1/2)n^2 + n/2 - n

= n^2 + n - n

= n^2

If that method was not to your liking, we can also show this result pictorially. Triangle numbers derive their name from fact that you can make them by adding up the number of dots that make different sizes of triangle, and square numbers from the number of dots that make up different sized squares. So all we need to do is make a square from two triangles of dots. If you try this out with coins or counters, or on paper, and make right-angled triangles, you should find that you can make a square from two triangles, but one has to be one counter smaller on each of its sides. Okay, that wasn't that rigorous a method for proving it, but it was a lot easier than doing a lot of algebra, wasn't it?

The Formula for Pascal's Triangle

The formula for Pascal's triangle is n!/(r!(n-r)!). This needs quite a lot of explaining. Firstly, what are n and r supposed to be in this formula? In this equation, n means the row in which the number you're trying to find the value of is. For the formula to work, we must count the row 1,1 as row 1. r is the number of numbers across your number is. In slightly better English, you count from left to right how far along the number you want to calculate is, and this gives you a value for r. The catch, however, is that we count the leftmost 1 as r=0, so you then have to subtract 1. Let's look at an example:

1 1

1 2 1

1 3 3 1

1 4 6 ? 1

So, what values would I use for n and r if I wanted to calculate the number in the position of the question mark? We are in the fourth row down, so n=4. Counting from left to right, the question mark is the fourth number along (okay, a question mark isn't a number, I know, but you get my point). However, we must remember that the first 1 in the row is r=0. Counting up from 0 gives r=3. So, in this example, we get 4!/(3!(4-3)!).

This is all very well, but we still don't know what this actually equals. However, have patience, as I am about to explain what all those "!" signs were for (no, they weren't just punctuation to show how amazing the formula is!)

To calculate n! you have to multiply together every positive whole number up to and including n itself. Perhaps a few examples will clarify this:

1! = 1

2! = 1 x 2 = 2

3! = 1 x 2 x 3 = 6

4! = 1 x 2 x 3 x 4 = 24

10! = 1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 x 9 x 10 = 3628800

It should now be clear how to use the formula for Pascal's triangle! I have given one example here just to you how cool it is:

Say I was walking down the street one day and suddenly needed to know (as one so often does) what the 5th number along on the 14th row of Pascal's triangle was. What do I do?

Firstly, I would have to decide what n and r are. n = 14 as I am interested in the 14th row, and r = 4, as we count along five numbers starting from 0. So, we get 14!/(5!(15-5)!)

= 87178291200/(24×3628800)=1001

So, the number I was looking for was therefore 1001.

This is definitely one of my favourite mathematical formulas. I suggest you try out a few examples yourself to get a feel for how it works. Then, you can try it on your friends and impress them with how fast you can calculate numbers in Pascal's triangle. Have fun!

The Fibonacci Sequence

The first two terms of the Fibonacci sequence are 1,1. From then on, each term is the sum of the previous two terms. This makes the third term 1 + 1 = 2, and the fourth term 1 + 2 = 3, and so on. The first ten Fibonacci numbers are shown below:

1, 1, 2, 3, 5, 8, 13, 21, 34, 55

A classic "real life" example of Fibonacci numbers is with rabbits. It goes a bit like this: I start with a pair of young rabbits in month 1. For their first month, they do not breed, as they are too young. However, for every month after this, they produce one new pair of young rabbits, which in turn grow up in a month and start breeding. If we call a junior pair of rabbits JJ and a senior pair SS, this is what happens:

Month

1. JJ = 1 pair

2. SS = 1 pair

3. SS + JJ = 2 pairs

4. SS + SS + JJ = 3 pairs

5. SS + SS + SS + JJ + JJ = 5 pairs

6. SS + SS + SS + SS + SS + JJ + JJ + JJ = 8 pairs

The number of pairs of rabbits gives the Fibonacci numbers! Luckily, in reality, there are certain factors that limit this growth in population. The rabbits will eventually die and stop producing new pairs, there will be limited food and space, etc. According to the sequence, by the end of two years, I would have over 46,000 pairs of rabbits, so it is a good thing that this is not really what happens in nature!

However, the Fibonacci sequence does have some closer links with nature. For example, flowers tend to have a Fibonacci number of petals. This is why it's so hard to find a four leaved clover! If you ever get really bored, you can count the number of petals on a daisy - it may not be exact, but it should be around 55 or 89! Other links with nature include the arrangement of seeds in sunflowers and pines in pine cones, and even the spirals of the shells of some animals.

One final interesting property of Fibonacci numbers is that they can be found in Pascal's triangle. They are perhaps the hardest pattern to spot of all the commonly discussed sequences that can be found in Pascal's triangle, but they are worth searching long and hard for, because they are one of the amazing patterns that can be found in Pascal's triangle! (If you want a hint, then don't look for the numbers themselves, but try adding together numbers from the triangle to make them).

N Choose R Notation

Before I even attempt to explain how to interpret "n choose r" notation, it's worth mentioning that mathematicians have many ways of writing it in equations:

1. nCr

Note that this version has a few different subversions. You can have:

i) n as a superscript and r as a subscript. Or even...

ii) Both of n and r as subscripts.

2. n

r (this version is usually written with a pair of long brackets around the n and r.

3. C(n,r)

Really, it's all a matter of taste - you may have thought that opinions didn't come into the equation with mathematics, but actually mathematicians quite enjoy this sort of thing - Some stick adamantly to one notation, convinced that what they are using is "official", and spend their free time trying to convert other mathematicians to their ways, and participating in heated debates, others enjoy switching between many different ways depending on what takes their fancy or what mood they're in, others may even have a different notation for each day of the week! So, it's up to you. To avoid offending anyone, however, I'll just steer clear of this controversial topic and just write n choose r in words each time.

Basically, n choose r just means the number of ways of choosing r objects from n distinct objects. So if I have four sweets, coloured red, yellow, green and blue, and you could choose any two of them, that would be 4 choose 2. But what does 4 choose 2 actually equal? We can list the different choices you could make (called combinations) below:

R and Y

R and G

R and B

Y and G

Y and B

G and B

This gives a total of 6 different choices you could make. Notice that order does not matter. So if you picked the red then the yellow sweet, then we are counting this the same as if you picked the yellow then the red sweet.

Below are a few examples which you can check yourself:

· 4 choose 1 is 4

· 4 choose 4 is 1

· 4 choose 0 is 1

· 5 choose 3 is 10

· 6 choose 3 is 20

After trying it out a few times by listing the combinations, you should begin to feel more comfortable at using n choose r notation. However, once you have understood how to do this, there is much more fun to be had. Did you know that you can save yourself time by using the formula n!/(r!(n-r)!), which also happens to be the formula for Pascal's triangle? Enjoy finding out more about this topic in the links below!

Simple Techniques to Find Math Answers

Learning math is a part of school many students would love to avoid. Caught in the difficulty and confusion that math often brings with it, students do not stop to think about how they use math in some form or the other, almost every day. Much of the difficulty associated with math is due to inadequate instruction in the classroom. Teaching math requires instructors to use a degree of creativity to ensure that the lessons are delivered to suit each student's aptitude and capability.

Since most teachers do not have the luxury of time, they tend to stick to tried and tested techniques, which leaves a lot of room for confusion in most students. Classroom sizes have also grown, making it difficult for each student to get individual attention. Fortunately, there is a lot that students can do to help themselves learn and understand math better.

Math is a logical and sequential subject. When we talk about finding the solution, it's not just about that final answer. The method and steps used are just as much part of the solution. Some problems can be solved in several ways while other questions require more detailed knowledge and practice in order to crack them. Whichever may be the case, learning math is a simple and very rewarding process, that teaches students problem solving skills they can apply to problems outside math.

Teach Yourself Math - It's Easier Than It Sounds!

As a first step to learning math, repeat the previous sentence to yourself a couple of times, emphasizing the 'math is simple part'. The reason why a lot of students rtruggle with the subject is that they have made it out to be an insurmountable mountain, which it certainly is not. Also, start with easy problems and questions when you practice. It's a sure shot way to build confidence in your own abilities. Once you change your attitude about math, you'll be solving math answers with much more interest.

Practice makes perfect is repeated often; so often that, perhaps it's lost it's punch! However it still holds very true for math. Practicing what you have learned the same day locks it into your memory for a long time. Practicing math does not have to be boring. Set a daily target to motivate yourself. Try adding variety by solving math problems from different books, playing math games, or, after you've gained some expertise, by setting a time limit for a particular number of questions. You can also try all these out with a friend, couple of times a week. It'll be a rewarding experience for you both. When the going gets tough, you can always try looking up free math answers online to sort things out.

Tips for Learning to Solve Equations

Solving equations often appears complicated, especially to students who have only started working with them. At first glance, linear equations and all the other forms of equations seem totally different from the arithmetic sums that students have become accustomed to. However, both arithmetic problems and equations involve finding a final solution which will make the problem statement true.

For equations, it involves solving for a variable that is represented by an alphabet, usually 'x'. Linear equations are the simplest form of math equations and can be solved quite easily since they they don't have any complicated variables with exponents, square roots, and the like. The good thing about solving them is that students have already learned everything they need to know. The basic step is to isolate the variable and solve the numerical part to arrive at a single answer which is the solution.

The best way to become an expert at solving equations is to work out different types of equations. Don't be in a rush to finish off one and jump to the next; take time to understand your progression from one step to the next. Understanding why you perform each operation will eventually help you learn different methods of solving equations. You will also be able to quickly determine which method to use for a particular math equation.

There are a few basic steps that can be applied to any equation. If you are solving word problems, you will have to formulate the equation yourself, based on the information provided in the question. Identifying the information that can be used is a valuable skill that will save time and bring clarity about the solution. Write down each step clearly so that the method is clear to you and to anyone reading your work. For word problems especially, write down the answer in words as well, using the same unit, if any, given in the question.

Learning to solve equations requires time and patience. Students need to work on it regularly in order to improve their skills. If you find that doing it by yourself is time consuming and not giving you the results you want, then consider getting help to learn better and more effectively. Math help is available at reasonable rates with good tutors, on the internet. Since it's easy to access and is available any time of the day or night, it's a great option for students who need a little extra help and a hand at practice.