AKANSHAs
on applying the above used concept for this question-The probability that event M will not occur is 0.8 and the probability that event R will not occur is 0.6. If events M and R cannot both occur, which of the following is the probability that either event M or event R will occur?
we are getting wrong answer-(11/25)
Hi AKANSHAs,
The prompt that you are asking about has been discussed here:
https://gmatclub.com/forum/the-probabil ... 20310.htmlThe math behind the two prompts is a bit different from one another, since the 'setups' are different. The prompt you're asking about tells us three Probability-based pieces of information:
1) The probability that Event M will NOT occur is 0.8
2) The probability that Even R will NOT occur is 0.6
3) Events M and R CANNOT BOTH occur.
We’re asked for the probability that Event M OR Event R will occur. While these types of probability questions are generally a bit harder in terms of difficulty, this particular prompt includes “causality” (which is a really rare concept in the Quant section) that actually makes the question easier to solve.
Normally, individual probabilities have NO impact on one another, but in this prompt, we are told that if Event M happens, then Event R CANNOT happen (meaning that there is an ‘absolute’ here and nothing to calculate). The same situation occurs if Event R happens (re: Event M automatically does NOT happen and there’s nothing to calculate).
Thus, there are just a couple of simple calculations to work through:
-The probability that Event M happens is 1 – 0.8 = 0.2
-The probability that Event R happens is 1 – 0.6 = 0.4
Thus, the probability that EITHER will happen is 0.2 + 0.4 = 0.6
GMAT Assassins aren’t born, they’re made,
Rich