Data Sufficiency

Economist GMAT

There are 4 times as many helicopters as there are fighter jets in Sangala's Army. What is the number of tanks in the Sangala's Army?

1) There are 15 tanks for every helicopter in Sangala's Army.
2) There are less than 200 tanks in Sangala's Army.

OA E

Let total helicopters = h
L et total Tanks = t
Let total fighter jets = f
For every fighter jets there are four helicopters so the ratio of fighter jets to helicopters is 1:4

Target Question
What is the number of tanks in the sangalas Army?
find the value of t.

Statement 1
There are 15 tanks for every helicopter in Sangala's Army.
For every helicopter, there are 15 tanks
So the ratio of helicopter to tanks =1:15
If h=2, then t= 15*2=30
If h=3, then t= 15*3=45
t is a depend variable that changes with reference to the value of h and this cannot provide a definite Answer to the target question hence, statement 1 is INSUFFICIENT.

Statement 2
These are less than 200 tanks in Sangala's Army
i.e t<200 the value of t could be any value between 0 and 99 and this does not provide a definite answer to the target question, hence statement 2 is not SUFFICIENT.


Combining both statement together
h : t = 1: 15 ------eqn i
t < 200 -----eqn ii
from the question stem
f : h = 1 : 4
Therefore, f : h : t = 1 : 4 : (15*4) = 1 : 4 : 60
If f = 2 then f : h : t = 2 : (4*2) : 15*(4*2) = 2 : 8 : (15*8) = 2 : 8 : 120
the value of t is dependent on the value of h while the value of h is dependent on the value of 'f'.
since the exact value of f is unknown the target question cannot be answered with certainty, so both statement together are not SUFFICIENT..

$$Answer\ is\ Option\ E$$