MathRevolution wrote:

The probability that event A occurs is 0.5 and the probability that event B occurs is 0.7. What is the probability that event A occurs but not event B?

1) Event A and event B are independent.

2) The probability that neither event A nor event B occurs is 0.15.

lets see the statements ..

1) Event A and event B are independent.

so P is P(A)*{1-P(B)}=0.5*(1-0.7)=0.15..

suff

2) The probability that neither event A nor event B occurs is 0.15

now NONE = 0.15...

but it is same as (1-P(A))(1-P(B))=(1-0.5)(1-0.7)=0.5*0.3=0.15..

this means the events are independent..

again suff

D

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1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372

2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html

3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html

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