GRE Question of the Day (July 28th)

Each of 100 balls has an integer value from 1 to 8, inclusive, painted on the surface. The number \({Nx}\) of balls representing integer x is defined by the formula \({Nx = 18 –(x – 4)^2}\).


What is the interquartile range of the 100 integers?

(A) 1.5

(B) 2.0

(C) 2.5

(D) 3.0

(E) 3.5