A certain sum amounts to ₹3,640 in 2 years  and ₹4,060 in 8 years at simple interest. Find the approximate rate percentage per annum ?

2%

Amount in 2 years = Rs.3640

Amount in 8 years = Rs.4060

S.I in 6 years = 4060 - 3640 = Rs.420

S.I. in 1 year = \(\frac{420}{6}\) = Rs.70

S.I. in 2 years = Rs.140

Principal = 3640 - 140 = Rs.3500

∴ Rate% = \(\frac{Interest}{Principal}\) × 100 

             = \(\frac{70}{3500}\) × 100

             =  2%