Asad wrote:
naveenhv wrote:
When n liters of fuel was added to a tank that was already 1/3 full, the tank was filled to 7/9 of its capacity. In terms of n, what is the capacity of the tank, in liters?
A. 10/9 n
B. 4/3 n
C. 3/2 n
D. 9/4 n
E. 7/3n
Hello Experts,
EMPOWERgmatRichC,
VeritasKarishma,
IanStewart,
chetan2u,
ArvindCrackVerbal,
GMATGuruNY,
GMATinsightCan I say the 'numerator' has to be 'factor' or 'multiple' of 9 (if 9 is considered as total capacity of anything) in the correct choices?
Also, in the choices A, B, and C says: the capacity is a
bit greater than that we add (n), but in choices D and E says: the capacity is
a bit more than double that we add (n). Could you explain a bit what's going on the answer choices?
Thanks__
Hi Asad,
This question can be solved relatively quickly in a couple of different ways, so it's really not necessary to try to think in terms of whether there's a quick, logical 'shortcut' to take advantage of.
We're told that when N liters of fuel was added to a tank that was already 1/3 FULL, the tank was filled to 7/9 of its capacity. We're asked for the capacity of the tank, in terms of N, in liters. This question can be solved by TESTing VALUES.
Since the tank ends up 7/9 full, it would make sense to choose a value for the FULL TANK that is a multiple of 9. In this case, the easiest value would be 9 (note: this is NOT the value of N). We can now set up an equation and solve for N...
N + (1/3)(9) = (7/9)(9)
N + 3 = 7
N = 4
Thus, we're looking for an answer that equals 9 when N=4. There's only one answer that matches...
You might also approach this question Arithmatically. Since 1/3 = 3/9... and we know that adding N liters of fuel increases the tank from "3/9 full" to "7/9 full", those N liters represent an increase of 4/9 of a tank. So how many of those "Ns" would it take to completely fill an empty tank?
(9/9) / (4/9) = 9/4
GMAT assassins aren't born, they're made,
Rich