Question

The simple interest on a sum of money will be Rs.600 after 10 years. If the principal is trebled after 5 years what will be the total interest at the end of the tenth year?

Answer 1

Formula used :

SI = [tex] \frac{PRT}{100} \\

Amount, A =P +SI [\tex]

Where P is Principal

R is rate of interest p.a.

T is time in years

Given:

SI after 10 years =Rs. 600

SI= 600 = [tex] \frac{10PR}{100} \\ \implies PR=6000 [\tex]

Amount after 5 years = 3 P

Amount = P + SI [tex]\\ \implies 3P = P+ \frac{5 PR}{100} \\ 2P=\frac{5 * 6000}{100} \\ P = \frac{300}{2} = 150

\\R= \frac{6000}{150} = 40% p.a.

\\ \therefore P =Rs.150

R =40%

SI after 10 years = 600

Amount after 10 years, A =P + SI = 150 + 600 =Rs. 750

Answer 2

SI = 600

T = 10 years

$SI =\frac{P* R * T}{100}$

$SI =\frac{P * R *10}{100}$

$SI =\frac{PR}{10}$

$600 =\frac{PR}{10}$

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  $=\frac{3P*R*5}{100}$

$=\frac{15P*R}{100}$

Where PR=6000

15×6000100=15×60=900  

∴ Total interest =300+900=Rs.1200