At what rate of simple interest per annum will Tk. 25,000 amount to Tk. 37,500 in 5 years?

Question: At what rate of simple interest per annum will Tk. 25,000 amount to Tk. 37,500 in 5 years?

Solution:
Principal, P = Tk. 25000
Total Amount, A = Tk. 37500
Time, n = 5 years

Simple Interest, SI = A - P = 37500 - 25000 = Tk. 12500

We know, SI = (P × n × r)/100
⇒ 12500 = (25000 × 5 × r)/100
⇒ 12500 = 250 × 5 × r
⇒ 12500 = 1250r
⇒ r = 12500/1250
⇒ r = 10

∴ Rate of simple interest = 10% per annum.