Given Principal = Rs 12000, Rate of Interest = 18% per annum and Time = 4 months = (4/12) = (1/3) years
We know that simple interest = (P × T × R)/100
On substituting these values in above equation we get
SI = (12000 × (1/3) × 18)/100
SI = (12000 × 1 × 18)/100 × 3
= Rs 720