Answer:
25%
Step-by-step explanation:
Let us first derive an equation for the productivity.
Given
No. of houses = 1 (Assumption)
Amount of Chemicals = 30 (10 x A, B, C)
Now the formula for productivity is as follow
Productivity % (P) = (Output/Input) * 100
Assuming the current productivity is 100%. We get the value for required output but using the value of 30 (Amount of Chemicals) as Input
Since we now know the value for desired output. We replace the value of input by 40, since 10 lbs of Chemicals have been increased per house.
The new Productivity is 75%
There is a reduction of 25% in productivity