Bunuel
The students in a certain class each joined a club: basketball club, soccer club, or swimming club. What fraction of the students joined swimming club?
(1) The number of the students who joined the basket club is three times the number of the students who joined the soccer club.
(2) The number of the students who joined the swimming club is twice the number of the students who joined soccer club or basketball club.
Let students joining the Basketball club be X
Let students joining the Soccer club be Y
Let students joining the Swimming club be Z
(1) The number of the students who joined the basket club is three times the number of the students who joined the soccer club.
Now X = 3Y
No information about swimming students.
Ratio required = Z/(X+Y+Z) => Z/(Z + 4Y)
--> Insufficient
(2) The number of the students who joined the swimming club is twice the number of the students who joined soccer club or basketball club
Now Z = 2(X + Y)
=> 2Z = X+Y
Ratio required = Z/(X+Y+Z) = Z/(2Z+Z) = Z/3Z
=>Ratio required = 1/3
--> Sufficient
IMHO Option B