ProbabilityWatch this thread
Digestive Digestive: 2/12 * 1/11 = 1/66
Chocolate Chocolate: 7/12 * 6/11 = 7/22
Ginger Ginger: 3/12* 2/11: 1/22
So, to find possibility of picking different types: 1 - (1/66 + 7/22 +1/22) = 41/66
Steve has 12 biscuits in a tin. There are 2 digestive, 7 chocolate and 3 ginger biscuits. Steve takes two biscuits at random from the tin. Work out the probability that he chooses two different types of biscuits.
digestive then chocolate
chocolate then digestive
digestive then ginger
ginger then digestive
chocolate then ginger
ginger then chocolate
so then just multiply the probabilities of each happening and add them together
ie first two
(2/12 x 7/11) + (7/12 x 2/11)
then continue with the rest of them....