How do you determine the number of ounces of pesticide to be added to a gallon of water?

How do you determine the number of ounces of pesticide to be added to a gallon of water?

• A. % pesticide in solution x 128 oz/gal
• B. 128 oz/gal x % pesticide in solution
• C. % pesticide in solution ÷ 128
• D. 128 oz/gal minus % pesticide in solution

Answer: (A)

Think of the final mixture as a fraction of pesticide in water. The amount of pesticide you add depends on the total volume of the mix, which in a gallon is 128 ounces, and the fraction of pesticide you want in that mix. So you multiply the final volume (128 oz) by the pesticide concentration expressed as a decimal. If the concentration is given as a percent, convert it to a decimal first (for example, 2% becomes 0.02). Then compute ounces of pesticide = 0.02 × 128 = 2.56 oz for a 2% final solution. In general, ounces of pesticide = (percent as decimal) × 128 oz. This is the correct approach because you’re scaling the desired fraction of pesticide by the total amount of liquid. Example: for a 5% target, 0.05 × 128 = 6.4 oz of pesticide.

Think of the final mixture as a fraction of pesticide in water. The amount of pesticide you add depends on the total volume of the mix, which in a gallon is 128 ounces, and the fraction of pesticide you want in that mix.

So you multiply the final volume (128 oz) by the pesticide concentration expressed as a decimal. If the concentration is given as a percent, convert it to a decimal first (for example, 2% becomes 0.02). Then compute ounces of pesticide = 0.02 × 128 = 2.56 oz for a 2% final solution.

In general, ounces of pesticide = (percent as decimal) × 128 oz. This is the correct approach because you’re scaling the desired fraction of pesticide by the total amount of liquid.

Example: for a 5% target, 0.05 × 128 = 6.4 oz of pesticide.