math
posted by kate on .
The area of a rectangular floor is 72 ft2. The length of the floor is 1 ft more than 3 times the width. How wide is the floor (rounded to the nearest whole number)?

area = width * length
length = 1+3*width
area = width * (1+3*width)
72 = w(1+3w) = w + 3w^{2}
3w^{2} + w  72 = 0
w = (1 + sqrt(865))/6 = 4.7
so, rounding up, w = 5'