Pascal Triangle

In mathematics, Pascal's triangle is a triangular
array of the binomial coefficients. It is named
after the French mathematician Blaise Pascal in
much of the Western world, although other
mathematicians studied it centuries before him
in India, Greece, Iran, China, Germany, and Italy.

• The set of numbers that form Pascal's triangle were known before Pascal.
However, Pascal developed many uses of it and was the first one to organize all the
information together in his treatise, Traité du triangle arithmétique (1653). The
numbers originally arose from Hindu studies of combinatorics and binomial
numbers and the Greeks' study of figurate numbers.
• The earliest explicit depictions of a triangle of binomial coefficients occur in the
10th century in commentaries on the Chandas Shastra, an Ancient Indian book
on Sanskrit prosody written by Pingala in or before the 2nd century BC. While
Pingala's work only survives in fragments, the commentatorHalayudha, around
975, used the triangle to explain obscure references to Meru-prastaara, the
"Staircase of Mount Meru". It was also realised that the shallow diagonals of the
triangle sum to the Fibonacci numbers. In 1068, four columns of the first sixteen
rows were given by the mathematician Bhattotpala, who realized the
combinatorial significance.
• At around the same time, it was discussed in Persia (Iran) by
the Persian mathematician, Al-Karaji (953–1029). It was later repeated by the
Persian poet-astronomer-mathematician Omar Khayyám (1048–1131); thus the
triangle is referred to as the Khayyam-Pascal triangle or Khayyam triangle in Iran.
Several theorems related to the triangle were known, including the binomial
theorem. Khayyam used a method of finding nth roots based on the binomial
expansion, and therefore on the binomial coefficients.

• Pascal's triangle was known in China in the early 11th century through the work of
the Chinese mathematician Jia Xian (1010–1070). In 13th century,Yang Hui (1238–
1298) presented the triangle and hence it is still called Yang Hui's triangle in China.
• Petrus Apianus (1495–1552) published the triangle on the frontispiece of his book
on business calculations in the 16th century. This is the first record of the triangle
in Europe.
• In Italy, it is referred to as Tartaglia's triangle, named for the
Italian algebraist Niccolò Fontana Tartaglia (1500–77). Tartaglia is credited with the
general formula for solving cubic polynomials (which may in fact be from Scipione
del Ferro but was published by Gerolamo Cardano 1545).
• Pascal's Traité du triangle arithmétique (Treatise on Arithmetical Triangle) was
published posthumously in 1665. In this, Pascal collected several results then
known about the triangle, and employed them to solve problems in probability
theory. The triangle was later named after Pascal by Pierre Raymond de
Montmort (1708) who called it "Table de M. Pascal pour les combinaisons"
(French: Table of Mr. Pascal for combinations) and Abraham de Moivre(1730) who
called it "Triangulum Arithmeticum PASCALIANUM" (Latin: Pascal's Arithmetic
Triangle), which became the modern Western name.[8]

• At the tip of Pascal's Triangle is the number 1, which makes up the zeroth row. The
first row (1 & 1) contains two 1's, both formed by adding the two numbers above
them to the left and the right, in this case 1 and 0 (all numbers outside the Triangle
are 0's). Do the same to create the
• 2nd row: 0+1=1; 1+1=2; 1+0=1. And the third: 0+1=1; 1+2=3; 2+1=3; 1+0=1. In this
way, the rows of the triangle go on infinitly. A number in the triangle can also be
found by nCr (n Choose r) where n is the number of the row and r is the element
in that row. For example, in row 3, 1 is the zeroth element, 3 is element number 1,
the next three is the 2nd element, and the last 1 is the 3rd element. The formula
for nCr is:
• n!
--------
r!(n-r)!
• ! means factorial, or the preceeding number multiplied by all the positive integers
that are smaller than the number. 5! = 5 × 4 × 3 × 2 × 1 = 120.
• The sum of any two adjacent elements in a row can be found between them on
the next row. Each row begins and ends with 1

• The sum of the numbers in any row is equal to 2
to the nth power or 2n, when n is the number of
the row. For example:
• 20 = 1
21 = 1+1 = 2
22 = 1+2+1 = 4
23 = 1+3+3+1 = 8
24 = 1+4+6+4+1 = 16

If the 1st element in a row is a prime number
(remember, the 0th element of every row is
1), all the numbers in that row (excluding the
1's) are divisible by it. For example, in row 7 (1
7 21 35 35 21 7 1) 7, 21, and 35 are all
divisible by 7.

• If a diagonal of numbers of any length is selected
starting at any of the 1's bordering the sides of
the triangle and ending on any number inside the
triangle on that diagonal, the sum of the numbers
inside the selection is equal to the number below
the end of the selection that is not on the same
diagonal itself. If you don't understand that, look
at the drawing.
1+6+21+56 = 84
1+7+28+84+210+462+924 = 1716
1+12 = 13

• If a row is made into a single number by using
each element as a digit of the number
(carrying over when an element itself has
more than one digit), the number is equal to
11 to the nth power or 11n when n is the
number of the row the multi-digit number
was taken from.

• Fibonnacci's Sequence can also be located in Pascal's
Triangle. The sum of the numbers in the consecutive rows
shown in the diagram are the first numbers of the
Fibonnacci Sequence. The Sequence can also be formed in
a more direct way, very similar to the method used to form
the Triangle, by adding two consecutive numbers in the
sequence to produce the next number. The creates the
sequence: 1,1,2,3,5,8,13,21,34, 55,89,144,233, etc . . . . The
Fibonnacci Sequence can be found in the Golden Rectangle,
the lengths of the segments of a pentagram, and in nature,
and it decribes a curve which can be found in string
instruments, such as the curve of a grand piano. The
formula for the nth number in the Fibonnacci Sequence is

• Triangular Numbers are just one type of
polygonal numbers. See the section
on Polygonal Numbers for an explaination of
polygonal and triangular numbers. The
triangular numbers can be found in the
diagonal starting at row 3 as shown in the
diagram. The first triangular number is 1, the
second is 3, the third is 6, the fourth is 10, and
so on.

• Square Numbers are another type of Polygonal
Numbers They are found in the same diagonal as the
triangular numbers. A Square Number is the sum of the
two numbers in any circled area in the diagram. (The
colors are different only to distinguish between the
separate "rubber bands"). The nth square number is
equal to the nth triangular number plus the (n-
1)th triangular number. (Remember, any number
outside the triangle is 0). The interesting thing about
these 4-sided polygonal numbers is that their name
explains them perfectly. The very first square number is
02. The second is 12, the third is 22 (4), the fourth is
32 (9), and so on.

• Connection to Sierpinski's Triangle
• When all the odd numbers (numbers not divisible by 2)
in Pascal's Triangle are filled in (black) and the rest (the
evens) are left blank (white), the recursive Sierpinski
Triangle fractal is revealed (see figure at near right),
showing yet another pattern in Pascal's Triangle. Other
interesting patterns are formed if the elements not
divisible by other numbers are filled, especially those
indivisible by prime numbers. Go here to download
programs that calculate Pascal's Triangle and then use
it to create patterns, such as the detailed, right-angle
Sierpinski Triangle at the far right.

• And the triangle is also symmetrical. The
numbers on the left side have identical
matching numbers on the right side, like a
mirror image.

• Pascal's Triangle can show you how many ways
heads and tails can combine. This can then show
you "the odds" (or probability) of any
combination.
• For example, if you toss a coin three times, there
is only one combination that will give you three
heads (HHH), but there are three that will give
two heads and one tail (HHT, HTH, THH), also
three that give one head and two tails (HTT, THT,
TTH) and one for all Tails (TTT). This is the pattern
"1,3,3,1" in Pascal's Triangle.

• Pascal's Triangle can also show you the
coefficients in binomial expansion:

• Choose any five colors. Assign a different color
to each number and shade
each block on the color
chart accordingly.
(See closure, below.)
•
• Print a blank Pascal Triangle grid from the student worksheets page.Color the top
three hexagons color 1. (Using black for color 1 provides a nice outline.)
• 4. To determine the color of the next row of cells, look at the last row:
• if there is only one cell above a cell, make that cell color 1.
• if there are two cells above a cell, use the chart to find the color to use.
• if the two cells above are both color 1, look at row 1 of column 1 on the chart for
the color to use. It is color 2.
• if the two cells above are colors 1 and 2, look at row 1 of column 2: it tells you to
use color 3.

• Notice that the gray cell is surrounded by 6 other cells.
These six cells make up the petals on Pascal's flower.
• Starting with the petal above and to the left of the gray
center, alternating petals are colored yellow and
numbered 5, 20, and 21.
• The three remaining petals around the chosen center
are colored orange and numbered 6, 10, and 35.
• The product of the numbers in the yellow petals is 5 x
20 x 21 = 2100.
• The product of the numbers in the orange petals is 6 x
10 x 35 = 2100.

• How many different 1-topping pizzas can you order when choosing from among 8
toppings?
•
• You can order 8 different 1-topping pizzas
• You can find the answer by listing the 8 possible pizzas, as shown above, or think:
how many different pizza combinations can I make by choosing 1 topping from a
set of 8 toppings?
• Using Pascal's triangle, find place 1 in row 8: 8 ways. [Remember that the first
number (1) in each row is place 0.]

• Now let's try a different approach to the problem. Antonio could have
helped the Pascalini's if he had asked the following questions:
•
Do you want anchovies?
Do you want extra cheese?
Do you want green peppers?
Do you want mushrooms?
Do you want olives?
Do you want pepperoni?
Do you want sausage?
Do you want tomatoes?
• How could this information help you to find the total number of different pizza combinations
that can be ordered?
• There are two possible answers to each of the 8 questions, yes or no. We can express the
total possible ways to answer these 8 questions as:
• 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 = 28 = 256
• Notice that the sum of the entries in the 8th row of Pascal's triangle can also be expressed as
• 28 = 256

• How many different 7-topping pizza combinations can you order from
a set of 8 toppings?
• You can order 8 different 7-topping pizzas:
You can find this answer by listing the 8 possible pizzas, as shown above, or think: how
many different 7-topping pizza combinations can I make from a set of 8 toppings?
Using Pascal's triangle, find place 7 in row 8: 8 ways.

• How many different pizza combinations can
you make using 2 toppings?
• You can order 28 different pizza combinations
when you choose 2 toppings from a set of 8
toppings

• How is the total possible number of 2-topping pizzas related to
the total possible number of 6-topping pizzas? Why?
• When you order a 2-topping pizza, you choose not to use 6
toppings.
When you order a 6-topping pizza, you choose not to use 2
toppings.
The number of possible choices is the same in each case: 28.
•
Can you find these numbers in Pascal's triangle? Look at row 8:

Pascal Triangle

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