For what percentage of profit per annum by which Tk. 12000 will be Tk. 17760 as profit-principal in 6 years?

Question: For what percentage of profit per annum by which Tk. 12000 will be Tk. 17760 as profit-principal in 6 years?

Solution:
Principal, P = Tk. 12000
Total Amount, A = Tk. 17760
Time, n = 6 years
Simple Interest SI = A - P = 17760 - 12000 = Tk. 5760

We know,
SI = Prn/100
⇒ 5760 = (12000 × r × 6)/100
⇒ r × 720 = 5760
⇒ r = 5760/720
∴ r = 8

So the profit percentage of per annum is 8%.