- #1
KevinItIs
- 12
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I have a GRE question of which there are two possible solutions, both of them seem correct to me, but I can't decide which line of reasoning is right. So Its my humble request to the people here to help me decide which one is correct and WHY.
.................
Given the probability of happening an event A is 0.80 and event B is 0.60.
Col A: The Probability of happening event A or B
Col B: 0.92
a)Col A is Greater.
b)Col B is Greater.
c)Both Col's are equal.
d)Answer cannot be determined from the information given.
.......................
Let P(A)= Probability of A happening = 0.80 ; P(B)= Probability of B happening = 0.60;
P(A')= Probability of A NOT happening = 0.20 ; P(B')= Probability of B NOT happening = 0.40;
Solution 1: P(A)P(B') + P(A')P(B) + P(A')P(B') = 0.8*0.4+0.2*0.6+0.8*0.6 = 0.32+0.12+0.48
=0.92. So on this basis, the answer is "C".
Solution 2: Prob that either A or B happens is 1 minus probability that neither happens. So
Prob = 1 - (0.20*0.40) = 0.20. So on this basis, the answer is "B".
.......................
Please Clarify which line of reasoning and hence the solution is correct.
.................
Given the probability of happening an event A is 0.80 and event B is 0.60.
Col A: The Probability of happening event A or B
Col B: 0.92
a)Col A is Greater.
b)Col B is Greater.
c)Both Col's are equal.
d)Answer cannot be determined from the information given.
.......................
Let P(A)= Probability of A happening = 0.80 ; P(B)= Probability of B happening = 0.60;
P(A')= Probability of A NOT happening = 0.20 ; P(B')= Probability of B NOT happening = 0.40;
Solution 1: P(A)P(B') + P(A')P(B) + P(A')P(B') = 0.8*0.4+0.2*0.6+0.8*0.6 = 0.32+0.12+0.48
=0.92. So on this basis, the answer is "C".
Solution 2: Prob that either A or B happens is 1 minus probability that neither happens. So
Prob = 1 - (0.20*0.40) = 0.20. So on this basis, the answer is "B".
.......................
Please Clarify which line of reasoning and hence the solution is correct.