Question

a set of 10 cards consists of 5 red cards and 5 black cards. the cards are shuffled thoroughly and i choose one at random, observe its color, and replace it in the set. the cards are thouruoghly reshuffled and i again choose a card at random, observe its color and replace it in the set. this is done a total of four times. let x be the number of red cards observed in these four trials. the mean of x is?

Answer 1

Four trials x 50% probability of a red each time = 2