GMATprep Q's - DS

Q1:
A & B have 16
B & C have 17
C & A have 18

Hence all we can say from the questions is A, B & C will have common not more than 16.

St1:Directly gives the answer as 9 hence sufficient
St2: Individual number of elements does not give the actual values which are in common so insufficient.

Hence Ans is A

Q2: The most important thing in this question is to understand it -
According to the question: 450<x<550 and 350<y<450
Hence => 800< x+y < 1000 => will be 800 if it lies btw 800 & 850; will be 900 if it lies btw 850 & 950 ; and finally will be 1000 if it is btw 950 & 1000

Statement 1: X < 500 doesnt provide an answer
St 2: Y <400 is not sufficient either

S1+S2: X+Y< 900 but from the question X+Y >800 hence this leads to either 800 or 900 as the answer hence Insuffi.

So choice is E