The difference between CI and SI for two years on sum of Rs.3500 at 20% per annum is:

120 140 150 125

140

20% = \(\frac{1}{5}\) ⇒ \(\frac{Diff.}{Principal}\) = \(\frac{1^2}{5^2}\) = \(\frac{1}{25}\) ⇒ 25R = 3500 ⇒ 1R = 140 ⇒ Difference = 1R = 1 × 140 = 140