Let the Principal ( sum deposited per month ) be P
Time Period (n) = 1 x 12 = 12
Total Amount Deposited = 12 P
Rate of Interest = 14 %
Interest = P × n×(n+1)2× 12 × r100
= P × 12×(12+1)2× 12 × 14100
= 0.91P
Maturity Value = Total Amount Deposited + Interest
Given , Maturity Value =₹ 6645
∴ 6645 = 12 P + 0.91 P
= 12.91 P
∴ P = 664512.91
P = ₹500