If the directions specify adding 3 pounds of wettable powder (WP) per 100 gallons of water, how much WP is needed for a 450-gallon tank?

To determine how much wettable powder (WP) is needed for a 450-gallon tank when the instructions indicate that 3 pounds are required per 100 gallons, you can use a simple proportional calculation.

First, establish how many 100-gallon increments are in 450 gallons. You can do this by dividing 450 by 100, which gives you 4.5, meaning there are four and a half 100-gallon increments in 450 gallons.

Next, multiply the number of increments(4.5) by the amount of WP needed for one increment (3 pounds). So, the calculation will look like this:

4.5 increments × 3 pounds per increment = 13.5 pounds of WP.

Thus, for a 450-gallon tank, 13.5 pounds of wettable powder is needed to meet the specified ratio in the directions. This calculation confirms that the correct option is indeed the one indicating 13.5 pounds, aligning perfectly with how to scale the instruction provided in terms of total volume.