Question

is how many years will rs 1000 become rs 2500 at 10%p.a.compound interest ?

Answer 1

use formula
A=p(1+r/100)^n

given
A=2500 Rs
p=1000 Rs
r=10%
n=?
now,
2500=1000(1+10/100)^n

2500/1000=(1+1/10)^n

5/2=(1.1)^n

2.5=(1.1)^n

take log both side
log(2.5)=log(1.1)^n
log(2.5)=nlog(1.1)

log(2.5)=0.3979
log(1.1)=0.04139

now,
n=0.3979/0.04139=9.61
hence ,
9.61 years