Real-Life Math
Kathy Messier, harbor master in Belfast, Maine, says, "I have to look at the whole picture and say, 'How will this [policy or choice] affect everybody?'" Sometimes that means sitting down to do some math.
You're a harbor master at an expanding marina. The dock expansions must float at very precise levels to insure buoyancy and usability. Foam blocks under the dock are used to do this balancing act.
Workers are building a wood dock that is 10 inches tall from top to bottom. The wood supplier tells you the material weighs 1,750 pounds. The top of the dock should be at least 14 inches above water when the dock is empty.
The foam blocks that will support this material are 10 inches tall. Each inch of block supports 73 pounds when completely submerged. When it's not underwater, each inch supports 61 pounds.
How many blocks will you need to support the dock to make sure the dock is 14 inches above the waterline?
Remember: you need 14 inches of total height, foam block plus dock, above the water. That means you need 4 inches of the foam block floating above the water.