Hi All,

We're told that the function f is defined by f(X) = (√X) - 10 for all positive numbers X and that U = f(T) for some positive numbers T and U. We're asked for T in terms of U. While this question might look 'scary', you can solve it by doing some basic work on your pad and TESTing VALUES.

To start, 'function questions' are essentially just about plugging in a value and determining the result (similar to graphing an individual points of an equation in co-ordinate Geometry).

We're told that U = f(T), so we'll pick a value for T, plug it into the given function and the result with be the value of U.

IF.....
T=4, then f(4) = (√4) - 10 = 2 - 10 = -8
U = -8

We're asked for T in terms of U, so we're looking for an answer that equals 4 when we plug in U = -8. There's only one answer that matches...

Final Answer: D

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