The simple interest on Rs.3500 increases by Rs.1400 when the time increases by 2 years. Find the rate of interest per annum.

20% 25% 22% 14%

20%

The increase in interest is due to time ⇒ \(\frac{3500\;×\;2\;×\;R%}{100}\) = 1400 ⇒ rate = 20%