Question

at what rate if interest per annum will simple interest be half of the principal in 5 years

Answer 1

let p is the principal r is the rate and t is the time
SI=P x r x t/100
according to question
SI=P/2 in 5 years

P/2=P x r x 5 /100

r=10%

Answer 2

let the principal =P = Rs x
time = T =5 yr
simple interest (I) = x/2
rate of interest = R

I= PTR/100

R = (100*I)/PT

R =(100*x)/(2*x*5)

R =10%