Question

A box contains 5 red and 5 green marbles. if 5 marbles are drawn without replacement, what is the expected number of red marbles

Answer 1

P( 5 reds, 1 green) = 6C3*P(drawing the red ones 1st, 2nd, 3rd 4th) = 6C5(5/10)(4/9)(3/8)(2/7)(1/6)(5/5) = 1/42