Bunuel
John will spend the summer in one of the houses either on Surf Street or Breaker Way. Surf Street has 1 landside house and 4 beachside houses, and Breaker Way has 1 beachside house and 2 landside houses. A sea turtle randomly lays eggs in front of a beachside house on Surf Street, and another sea turtle randomly lays eggs in front of a beachside house on Breaker Way. What are the probabilities that a sea turtle lays its eggs in front of John`s house, depending on which street he lives on?
I. 1/5
II. 4/15
III. 1/3
A. I only
B. II only
C. III only
D. I and III only
E. I, II and III
If John is staying at a house on Surf Street, then the probability is 4/5 x 1/4 = 1/5 that the turtle will lay eggs in front of John’s house (notice that 4/5 is the probability John will stay at a beachside house and 1/4 is the probability the turtle will lay eggs at the house in which John is staying).
If John is staying at a house on Breaker Way, then the probability is 1/3 x 1/1 = 1/1 that it will lay eggs in front of John’s house (notice that 1/3 is the probability John will stay at a beachside house and 1/1 is the probability the turtle will lay eggs at the house in which John is staying)..
Answer: D
I'm sorry, I still don't understand this, why are we not adding the two 'OR' probabilities here? I know that's not an answer option, but that's where I got stuck. Since John will EITHER live in Surf Street OR in Breaker Way.