Question 659080
Percentage = part/whole

Part:
You are adding 1 ounce, but only half of it is malathion. So the part is 0.5 oz.


Whole:
you have added 1 oz to 128 oz so the whole is 129 oz


percentage = 0.5 ounce/129 oz
pct = 3.9% (this is rounded)



(Bottom line: don't use toxins like malathion.)