word problem

[sud21]

There are some green balls and blue balls in a box. what is the total number of the balls?
1) The number of the green balls is 1/3 of the number of the total balls
2) If one green ball is taken out, the remaining green balls are 1/5 of the balls in the box.

[Anurag@Gurome]

There are some green balls and blue balls in a box. what is the total number of the balls?
1) The number of the green balls is 1/3 of the number of the total balls
2) If one green ball is taken out, the remaining green balls are 1/5 of the balls in the box.

Let Green balls = G, blue balls = B and total balls = T
G + B = T
(1) G = T/3, the info in this statement does not help to find the total balls; NOT sufficient.

(2) G - 1 = (T - 1)/5, there can be many possibilities according to the given info; NOT sufficient.

Combining (1) and (2), we have
T/3 - 1 = (T - 1)/5
5T - 15 = 3T - 3
2T = 12 implies T = 6; SUFFICIENT.

The correct answer is C.