Gmat Prep. Gmat experts pls explain with tabular format

[alltimeacheiver]

Of the students who eat in a certain cafeteria , each student either likes or dislikes lime beans and each student either likes or dislikes brussel sprouts. Of these students,2/3 dislike lima beans ; and of those who dislike lima beans , 3/5 also dislike brussel sprouts. How many of the students like brussel sprouts but dislike lima beans?

a. 120 students eat in the cafeteria
b. 40 of the students like lima beans

[cans]

2/3 l' (dislike lima beans)
1/3 l
(2/3)*(3/5) l'b' (dislike both beans and sprouts)
2/5 l'b'
also (2/3)(2/5) l'b = 4/15
bl'??


A) total 120. 4/15 of 120 = 32 sufficient
B) l=40. thus 1/3 of x = 40 or total=120
Sufficient
IMO D

[bijoyajj]

draw a table with one grid for L & B (horizontally) and like & dislike vertically.. just fill in.. You can see that once we get the total no of ppl.. grid gets solved .. So if ever any choice is telling about any number then it gets solved as we can deduct total from it.. Both choices suffice.

[mehrasa]

IMO: D