1. Grade 8 | Unit 8.3 | Page 9
Unit 8.3
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More on probabilities
• There is no pattern in gambling games of chance (like the Lotto, coin
tossing, dice throwing, card-picking, slot machines) on which to base
predictions. You can, however, calculate the likelihood of a particular
outcome and you can also calculate your chances of winning. The number
assigned to this likelihood is called a probability.
• Probability lies between 0 and 1, where 0 = impossible and 1 = certain.
Probabilities may be represented by fractions, e.g., 1/2, (a 1 in 2 chance
that an event will occur - like heads or tails), 1/6, (for dice) etc; or
alternatively as decimal numbers between 0 and 1, e.g., 0.5, 0.25,
0.66666, etc.
• The general rule for calculating the probability of an outcome of an event
(like picking a card) is:
p = n/t
p stands for probability,
n for the number of favourable outcomes, and
t for the total number of all possible outcomes
• How many cards in a deck?
• How many 9 are there in a deck?
• What do you think the chances are of picking or drawing 9 from a deck
(no peeking beforehand! The draw must be a random process!)
• What is the probability of picking any card from the deck?
• What is the probability of drawing any red card ( and o) from the deck?