The function floor(x) + floor(2x) + floor(3x) + floor(4x) takes on different values for 0 <= x <= 1 if and only if the fractional part {x} of x satisfies 0 <= {x} < 1/4. The different values that {x} can take on in this range are 0, 1/4, 2/4, 3/4, and 1. Therefore, the function floor(x) + floor(2x) + floor(3x) + floor(4x) takes on 1 + 4 = 5 different values in the range 0 <= x <= 1.
