Answer : 12%
explanation :
Let the sum of money be P(which is the principal value) and rate of interest be R.
According to the question,
Amount (principal +simple interest) = 8P/5
Time (T) = 5 years
Simple interest (SI) = PRT/100
SI = 5PR/100
Amount = P +SI
8P/5 = P+(5PR/100)
8P/5 = P(100+5R)/100
160 = 100 +5R
5R =60
R = 12
Therefore, rate of interest = 12% p.a.
