Take P=x, Then amount is 5x(5 times of x). Time =100 years(time is given)
we know that SI= Amount-principal
Therefore, SI=5x-x = 4x
now the formula to find rate is :-
R=SI x 100/P x T = (4x x 100/x.100)%=4%
Let p= Rs.1
R=4% and Time=100 years
SI=Rs (1 x 4 x 100)/100 = Rs 4
Amount = P + SI = Rs 1 + Rs 4 = Rs 5, which is 5 times of 1.
Hence verified too.