Calculate the probability that the building is protected by NO alarm. Subtract from 1.0 gives you the probability required.
P(≥1)=1-(1-80%)*(1-70%)
Let P(W)=x
Probability of picking two whites
P(WW)=x²=0.49
x=?
Two questions:
1. Assume a building has two independent security alarm systems. The first system works for 80% of the time and the second works 70% of the time. What percentage of time is the building protected by at least one security alarm system? Please explain.
2. There are 100 ping pong ball in a bag. some of them are white and the rest are yellow. Latoya is asked to randomly pick out 2 ping pong balls (1 at a time with replacement). She finds out that the chance for her to get 2 white balls is exactly 49%. How many white balls are in the bag?
3 answers
got it thank you very much
You're welcome!
2 answers