Post on 17-Dec-2015
Calculate the number of outcomes
)!(!
!
rnr
n
r
n
We can calculate the number of possible outcomes instead of making a list, by using a formula.
n = total
r = total number chosen
r
ncan also be written as nCr.
Example
3 cards are dealt from an ordinary pack of playing cards.
a) Calculate the probability that 3 kings are dealt.
b) Calculate the probability that 2 jacks and 1 queen are dealt.
We must first calculate the total number of combinations of choosing 3 cards.52C3 = 22100
(This is the denominator throughout the question.)
b) Deal 2 jacks and 1 queen = 4C2 x 4C1 = 24
P(Deal 2 jacks and 1 queen) = 24 . = 6
22100 5525
a) Ddeal 3 kings = 4C3 = 4
P(deal 3 kings) = 4 . = 1 . 22100 5525