Solution:Average Monthly Income (old system) = 77
So, Total Income of 173 families/14 = 77
So, Total Income of 173 families = 77 × 14
Now, Average Monthly Income of 173 families (new system)
Total Income/12 = 77 × 14/12 = 89.83 fasios
Now, Average Monthly expenditure (old system) = 21
So Average Monthly Expenditure (new system)
= 21 × 9/12 = 15.75
Total Savings (old system) = 77 - 21 = 56
Total Savings (new system) = 89.83 - 15.75 = 74.08
%change = (74.08 - 56)/56 × 100 = 32.3%