probability + venn diagrams

Q.) The waiter at an expensive resturant has noticed that 60% of the couples order desert and coffee. However, 20% of the couples who order desert dont order coffee. what is the probability that the next couple the waiter seats will not order desert?

A.) 20%
B.) 25%
C.) 40%
D.) 60%
E.) 75%

OA ...B

Discussed many times in the forums. May be this is the fastest approach. h(100) + 1 = (2*4*6*8*10*...*100) + 1 = 2*(1*2*3*4*5*...*50) + 1 Thus when [h(100) + 1] is divided by any integer (including all the primes) less than or equal to 50, it'll leave a remainder of 1. Thus p must be greater than 50...