# Thread: Probability problem long one

1. ## Probability problem long one

Suppose that the probability that an individual has been exposed to high levels of carbon monoxide in their lifetime is 0.06 and that the probability that they have been exposed to high levels of nitrogen dioxide is 0.03. What is the probability that an individual has been exposed to either high levels of carbon monoxide or high levels of nitrogen dioxide but not both?

All i know is that i have to add them because they asked for "or" then i have to subtract because it is a "not both" problem but i have no idea what to subtract

Thank you for your help guys

2. Originally Posted by justiceflare33
All i know is that i have to add them because they asked for "or" then i have to subtract because it is a "not both" problem but i have no idea what to subtract
Hi,
you are right, but then why don't you just substract the probability that both high exposures happen? Assuming that they are independent of each other, the probability of high levels of both gases is the product of their probabilities. So you end up with a probability 0.06 + 0.03 - 0.06*0.03.

Laurent.