The percent of the decrease in the average class size will be 40.
The quantity of anything is stated as though it were a fraction of a hundred. A fraction of 100 can be used to express the ratio.
Given data;
The average class size a decade ago,(initial value,u = 20 students
The average class size at present,(final value),v= 12 student
Percentage decrement = ( initial value-Final value )/final value
%=[(u-v)/v]×100
% =[(12-40)/40]×100
% = 40
Hence, the percent of the decrease in the average class size will be 40.
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