The amount of stain needed to cover a wood surface is directly proportional to the area of the surface. If 3 pints are required to cover a square deck with a side of 7 feet, how many pints of stain are needed to paint a square deck with a side of 10 feet 6 inches?

For 10 feet and 6 inches,

12 inches = 1 foot, therefore 6 inches = 6/12 foot = 0.5 foot

10 feet 6 inches = 10 + 0.5 = 10.5 feet

7 feet required 3 pints

1 foot would have required (3/7) pints

10.5 feet will then require: (3/7) * 10.5 = 4.5 pints.

Therefore 10 feet and 6 inches will require 4.5 pints.