Rs. 4200 amounts to Rs. 5712 in 4 years. If rate of interest is increased by 3%. What will be the amount?

S.I = Principal x Rate x Time / 100
∴ Amount - Principal = Principal x Rate x Time / 100
⇒ 5712 - 4200 = (4200 x Rate x 4) /100
⇒ 1512 = 42 x 4 x Rate
Rate = 1512 / (42 x 4) = 9%
On increasing 3%, new rate of interest = 9 + 3 = 12%
Simple interest on new rate = (4200 x 12 x 4) / 100 =Rs. 2016
Amount = Principal + Interest = 4200 + 2016 = Rs. 6216