Question

In how many years a sum will be thrice of it at the rate of 10% per anum

Answer 1

(n - 1) x 100 = rt

n = Number of times the amount will become in t years at r% per annum SIMPLE INTEREST.

Apply to given problem :-

n = 3, r = 10, t = ?

( 3 - 1 ) x 100 = 10 x t

t = 200/10 = 20 Years

Cheers !!!!!!

NOTE : This relation holds good only for SIMPLE INTEREST.

****** Conventional method *********

Let the number of years required = t

Let Principle = P

Amount = 3P

Interest earned = 3P - P = 2P

Now using formula SI = PRT/100, we have

2P = P x 10 x t/100

2 = 10 x t/100

t = 200/10 = 20 years

Cheers !!!!

Answer 2

si = x , rate =10% , p=x x+x=2x , then t= 2x × 100/ 10 =20year answer