Question

a certain anount of money lent out at certain interest doubles itself in 15years, then in how many years the amount will triple itself

Answer 1

principal =x
Interest =x 
x= x*8*r/100
r=100/8

--------------= 
2x= x*n*100/8 *1/100
2=100n/800 
1600=100n
n= 16 years