Final answer:
The rate of interest that earned $2,800 as interest on a sum of $28,000 in 2 years is 5%, calculated using the simple interest formula I = PRT and solving for R.
Step-by-step explanation:
The student is asking how to calculate the rate of interest that earned $2,800 as interest on a sum of $28,000 in 2 years. To find the interest rate, we use the formula for simple interest: I = PRT, where I is interest, P is principal, R is the rate of interest per year, and T is time in years.
To solve for R, we rearrange the formula to R = I / (PT).
Plugging in the given values:
- I = $2,800 (Interest earned)
- P = $28,000 (Principal amount)
- T = 2 years (Time period)
The calculation for the rate of interest R is as follows:
R = $2,800 / ($28,000 × 2)
R = $2,800 / $56,000
R = 0.05 or 5%
Therefore, the rate of interest that earned $2,800 on $28,000 in two years is 5%.