A box contains 3 plain pencils and 9 pens. A second box contains 7 color pencils and 3 crayons. One item from each box is chosen at random. What is the

Question

probaility that a plain pencil from the first box and a color pencil from the second box are selected?

Answer 1

The first box contains 12 items total.  There are 3 plain pencils, so the probability of choosing a plain pencil is 3/12 = 1/4 (number of chosen item/total items).

 

The second box contains 10 items total. There are 7 color pencils, so the probability of choosing a color pencil is 7/10 (number of chosen item/total items).

 

The probability of choosing a plain pencil OR a color pencil (independent events) is additive = 1/4 + 7/10 = 38/40

 

The probability of choosing a plain pencil AND a color pencil (dependent events) is multiplicative = 1/4 x 7/10 = 7/40