My take.. C

I did it this way...

Let 'a' be the number of round,scented candles
Let 'b' be the number of round,unscented candles
Let 'c' be the number of square,unscented candles
Let 'd' be the number of square,scented candles


Required -- the probability that a candle selected randomly from the box will be unscented i.e., b+c/a+b+c+d

Given -- 60% of the candles are round --> a+b/a+b+c+d = 60/100
which leads to 2(a+b) = 3(c+d) ------------- (i)

----------------------------------------------------------------------------

1) If a candle is scented, it has an 80% chance of being round

--> a/a+d = 80/100 --> a = 4d ------------ (ii)

Using (i) and (ii), b+c/a+b+c+d reduces to c-d/c+d, which cannot be determined

Hence, (1) alone is not sufficient


2) If a candle is square, it has a 25% chance of being scented

--> d/c+d = 25/100 --> c = 3d -------------- (iii)

Using (i) and (iii), b+c/a+b+c+d reduces to b+3d/10d, which cannot be determined

Hence, (2) alone is not sufficient


Combining both, if (iii) is used in c-d/c+d(arrived at using (i) and (ii)), we get 3d-d/3d+d = 1/2

Hence, both the statements together are needed to arrive at the answer