Explanation

Here,
Sum = Principal (p)
Simple Interest (S.I.) = ₹ 6900
Time (t) = 23 years
Rate (r) = 8 % p.a.
We know,
S.I. =\frac{p\ \times\ r\ \times\ t}{100}
Or, P =\frac{S.I.\ \ \times\ 100}{r\ \times\ t}
Putting the value, we get,
P =₹\;\frac{6900\times100}{8\times23}
\rightarrow P =₹ 3750
So, the principal amount is ₹ 3750
Ans: The sum is ₹ 3750 yield a simple interest of ₹ 6900 in 23 years at 8% p.a. rate of interest.

Another variant of this particular question is:
1. Calculate the principal sum required to yield a simple interest of ₹6900 in 23 years at an 8% per annum interest rate.
2. Find out the initial amount of money needed to generate a simple interest of ₹6900 over a period of 23 years at an interest rate of 8% per annum.
3. Determine the principal sum that would yield a simple interest of ₹6900 after 23 years with an 8% per annum interest rate.
4. What is the principal amount required to accrue a simple interest of ₹6900 over 23 years at a rate of 8% per annum?
5. Calculate the sum of money needed to produce a simple interest of ₹6900 over a 23-year period with an annual interest rate of 8%.