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Flashcards in Other Deck (8):
0

What does the symbol ! mean?

! means that you have to multiply that number by all the numbers that come before it.
Ex: 5!=5x4x3x2x1
20x3x2x1
60x2x1
120x1
120

1

8!/3!x5!=?

8x7x6x5x4x3x2x1
________________
3x2x1x5x4x3x2x1

Since there is 5x4x3x2x1 on each side, you can take them off.
8x7x6
_____
3x2x1

8x7x6
_____
6 You can take off the 6s off each side.

8x7
56

2

How do you write a decimal number whose decimal digits go on for ever in a definite pattern?
Ex:1.333333333333333333333...

You write:
__
1.33

3

What does the symbol ~ mean?

When you see the symbol ~ in front of a number, it means the number equals about that.
Ex:pi ~ 3.14

4

What is a prime number?

A prime number is a number that is only divisable by itself and 1.
Ex:3,5,7,11,13...

5

What is the Fibonacci sequence?

It is a sequence invented by Leonardo Fibonacci. He was studying the reproduction of rabbits and noticed a strange sequence.
A pair of rabbits make no offspring in one month, a pair in the second month and another pair the third month, another the fourth...
At first there was one pair of rabbits. Then there was one new pair.
Then 2 new pairs. The sequence went:
1,1,2,3,5,8,13,21,34,55...
Fibonacci noticed that if you add the last two numbers you have, you get the next number in the sequence.
Ex:34+55=89
The next number in the sequence is 89.

6

What is the golden number?

The golden number is commonly called phi. Like pi,it was discovered by the Greeks. It is equal to 1.618...
Many things are concerned with phi. The golden rectangle (a rectangle who was considered as being the nicest to look at, not too fat, not too thin) has sides of 1 on phi. If you divide a number from the Fibonacci sequence by the one that comes before it, you get closer to phi the bigger the numbers you divide.
Ex:34:21=1.619

7

How do you draw a golden rectangle?

Draw a square. Put your compass point on a corner, put the other end on the opposite corner and draw a circle. Extend the side on which you put your compass point until it reaches a point in the circle.
Extend the side that is parallel to that also. Finally, draw a line perpendicular to both sides and erase the line separating your square from the new rectangle. You will have a golden rectangle.
The exciting bit is that if you had erased the square and left the little rectangle, it would have made a golden rectangle too!