Probability Question

Question

Cards numbered 1-10 are colored red and cards numbered 11-20 are colored black. What is the probability of drawing a card with an even number, or drawing a black card?

Answer 1

entire set {1,2,...,20} 20 members

even set {2,4,6,...,18,20} 10 members

black set {11,12,...,20} 10 members

even AND black set {12,14,16,18,20} 5 members

 

P(even OR black) 

= P(even) + P(black) - P(even AND black)

= 10/20 + 10/20 - 15/20

= 5/20

= 1/4