Penalty for 1st day= 200
Penalty for 2nd day=250
Penalty for 3rd day = 300
Hence the series is
200,250,300...
Since difference is the same, it is AP
Common difference=d=50
We need to find total penalty if work is delayed by 30 days
i.e. we need to fins s₃₀
We know that
Putting n= 30 , a = 200, d = 50
30/2(2x200+(30-1)x50)
=15(400+1450)
=15x1850
=27750
Hence,the total penalty if works is delayed by 30 days is Rs 27750