The function f is defined as follows: for any 3-digit integer (written

Hi All,

This question can be beaten by TESTing VALUES and using the information that you're given to limit the possibilities.

We have 3 variables (X, Y and Z) that form a 3-digit number: XYZ

**NOTE: when we see XYZ that DOES NOT mean multiply X, Y and Z**

The function we're given is this:
f(XYZ) = (2^X)(3^Y)(5^Z)
So, if we have the three digits, then we just just plug them into the function and get a value.

Next, we're told that C and K are both 3-digit numbers and that f(C) = 16(f(K). Now, THAT is interesting because for a number to be 16 times another number, we're going to have to deal with powers of 2 (16 = 2^4). Notice how the math involved uses 2^X......

I'm going to keep things as simple as possible:

K = 100 This is the smallest 3 digit number that is available and it will make our math easy.

f(K) = (2^1)(3^0)(5^0) = (2)(1)(1) = 2

Now we need a result that is 16 times that.... so we have to take the first digit (the 'power' of 2) and raise it, while keeping everything else the same....

C = 500

f(C) = (2^5)(3^0)(5^0) = (32)(1)(1) = 32

Now we have two 3-digit numbers that fit what we're told (and it turns out that they're the ONLY numbers that would fit the given scenario)

C - K =400

Final Answer:

GMAT assassins aren't born, they're made,
Rich