A certain sum on simple interest becomes Rs. 49600 in 3 years and Rs. 56000 in 5 years. If the rate of interest had been 2% more, then in how many years sum had been tripled?

20 years

56000 - 49600 = 6400                      

SI = \(\frac{6400}{2}\) = 3200                       

3SI = 9600                                                     

P = A - (SI of 3 years)                                       

P = 49600 - 9600 = 40000                               

R = \(\frac{3200 }{40000}\) × 100% = 8%

Now,

A= 3P = P + 2P (SI)

Increased rate = 10%

SI = PRT

2P = \(\frac{P × 10 × T }{100}\)

T = 20 years