The Simple Interest on a sum of money will be Rs.600 after 10 years. If the principal is increased three times after 5 years, what will be the total interest at the end of 10 years?

Given that

SI = 600

T = 10 years

$$SI=\frac{(P)\times(R)\times(T)}{100}$$

$$SI=\frac{(P)\times(R)\times(10)}{100}$$

$$SI=\frac{(P)\times(R)}{10}$$

PR = 6000  

Given that the simple interest for 10 years = Rs.600  

Then for 5 years, it will be Rs.300

If the principal is tripled for next 5 years, then the SI for next 5 years will be  $$=\frac{3P\times(R)\times5}{100}$$

Where PR=6000

$$\frac{15×6000}{100}=15×60=900$$

∴ Total interest =300+900=Rs.1200