Find the rate of which 280 naira will earn 21 naira simple interest for 2 and half years

To find the rate at which 280 naira will earn 21 naira simple interest for 2 and a half years, we can use the formula:

Simple Interest = (Principal x Rate x Time) / 100

Where:
Principal = 280 naira
Simple Interest = 21 naira
Time = 2.5 years

Let's substitute the values into the formula and solve for Rate:

21 = (280 x Rate x 2.5) / 100
21 = 7 x Rate
Rate = 21 / 7
Rate = 3

Therefore, the rate at which 280 naira will earn 21 naira simple interest for 2 and a half years is 3%.