# Probability is the Likelihood, or chance, that an event will occur, often expressed as odds, or in mathematics, numerically as a fraction or decimal.

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Introduction

Probability

Probability is the Likelihood, or chance, that an event will occur, often expressed as odds, or in

mathematics, numerically as a fraction or decimal.

In general, the probability that n particular events will happen out of a total of m possible

events is n/m. A certainty has a probability of 1; an impossibility has a probability of 0. Empirical

probability is defined as the number of successful events divided by the total possible number of

events.

In tossing a coin, the chance that it will land `heads´ is the same as the chance that it will land

`tails´, that is, 1 to 1 or even; mathematically, this probability is expressed as 1/2 or 0.5. The odds

against any chosen number coming up on the roll of a fair die are 5 to 1; the probability is 1/6 or 0.1666...

. If two dice are rolled there are 6 ´ 6 = 36 different possible combinations. The probability of a double

(two numbers the same)

Middle

1/3 + 1/3 + 1/3 = 1

To find out the probability of two or more mutually exclusive events occurring, their individual

probabilities are added together. So, in the above example, the probability of selecting either a blue

marble or a red marble is 1/3 + 1/3 = 2/3 The probability of two independent events both occurring is

smaller than the probability of one such event occurring. For example, the probability of throwing a

three when rolling a die is 1/6, but the probability of throwing two threes when rolling two dice is 1/36.

Probability theory was developed by the French mathematicians Blaise Pascal and Pierre de

Fermat in the 17th century, initially in response to a request to calculate the odds of being dealt various

hands at cards. Today probability plays a major part in the mathematics of atomic theory and finds

application in insurance and statistical studies.

Pascal, Blaise (1623-1662)

Blaise Pascal was a French philosopher and mathematician. He contributed to the development

Conclusion

volumes.

Calculating machine

Between 1642 and 1645, Pascal constructed a machine to carry out the processes of addition

and subtraction, and then organised the manufacture and sale of these first calculating machines. At

least seven of these `computers´ still exist. One was presented to Queen Christina of Sweden in 1652.

Pascal was born in Clermont- Ferrand. In Paris in his teens he met mathematicians Descartes and Fermat.

From 1654 Pascal was closely involved with the Jansenist monastery of Port Royal. He defended a

prominent Jansenist, Antoine Arnauld (1612-1694), against the Jesuits in his Lettres

provinciales/Provincial Letters 1656. His Pensées 1670 was part of an unfinished defence of the

Christian religion. His last project was to design a public transport system for Paris, which was

inaugurated in 1662. Pascal's pioneering work on fluid pressure laid the foundations for both hydraulics

and meteorology. In his honour, the SI unit for pressure is called the pascal. It is equal to one Newton

per square metre. (©Helicon Publishing Ltd, printed from the Hutchinson Educational Encyclopedia,

2000)

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