8 pens in a bag, 3 blue, 5 red. 2 taken out at random, without replacement. Probability they are the same colour?
Either both blue or both red. 'OR' rule - add probabilities.Blue - first blue and second blue - 'AND' rule - multiply probabilities. 3/8 x 2/7 (as not replaced) = 6/56 = 3/28 (multiply top and bottom)Red - 5/8 x 4/7 = 20/56 = 5/143/28 + 5/14 = 3/28 + 10/28 = 13/28
AS
