ebaines, in the second problem the OP is saying (because 1+ 2+ 3+ ...+ 31+ 32= 32(33)/2= 495) the probability of choosing 1 is 1/495, the probability of choosing 2 is 2/495, etc.

The probability of 32 being chosen is 32/495 so the probability of it NOT being chosen is 1- 32/495= 464/495. Assuming "sampling

**with** replacement" (sampling without replacement would be very difficult- the probabilty of a specific number being chosen after another has been removed will depend stongly on what number had been removed) the probability 32 is not chosen in four trials is

approximately.