Find the simple interest on 280naire for two and half years at 3% per annum

Simple interest = (P x R x T)/100

Where,
P = Principal amount = 280 naire
R = Rate of interest per annum = 3%
T = Time period = 2.5 years

Putting the values in the formula, we get:
Simple interest = (280 x 3 x 2.5)/100
= 21 naire

Therefore, the simple interest on 280 naire for two and half years at 3% per annum is 21 naire.