Answer
P(three bedrooms) =$\frac{800}{2000}$ = 0.4
P(four bedrooms) =$\frac{600}{2000}$ = 0.3
P(three or four bedrooms) = 0.3+0.4 = 0.7
This probability is not equal to 1.0 because there are other possibilities of number of rooms other than three and four.
Work Step by Step
no