A farmer has 190 L of 70% herbicide solution. How much of a 95% herbicide solution should he add in order to get an 80% herbicide solution?

Question

A farmer has 190 L of 70% herbicide solution. How much of a 95% herbicide solution should he add in order to get an 80% herbicide solution?

Answer 1

The percentage of herbice in solution can be expressed as herbicide * 100/ total liters. The herbicide in solution is the total herbicide as found by multipling the ( percentage / 100) by the volume. If L is the unknown liter addition of 95 % herbicide then the total herbicide is 0.7( 190) + 0.95 L. The total volume is 190 + L. Putting this all together: [ 0.7 (190) + 0.95 L ] / ( 190 + L) = 0.8

Multiply each side by 190 + L: 0.7 (190) + 0.95 L =0.8 ( 190 + L)

Multiply thourgh : 0.7 (190) + 0.95 L = 0.8 (190) + 0.8 L

Subtract 0.7 (190) from both sides: 0.95 L = 0.1(190) + 0.8L

Multiply through: 0.95 L = 19 + 0.8 L

Subtract 0.8 L from both sides: 0.15 L = 19

Divide by 0.15 : L = 126.67 with the 6 repeating

or 126 2/3 L