The interest rate needs to be 9.8% for the sum of $4000 to compound to $240,000
Step-by-step explanation:
Since the interest compounds itself, hence the question concerns the compound interest.
Details provided-
Principal (Initial contribution)- $ 4000
Amount (Expected amount)- $ 240,000
Time period- investment started at 22 years and would continue until 66 years.
Time period= 66-22 years= 44 years
Rate of interest=
We know that for compound interest-
⇒Amount= principal (1+rate/100)ⁿ
Substituting the values if Amount, principal and time ("n") in the above equation
240,000= 4000 (1+rate/100)
⁴⁴
240,000/4000= (1+rate/100)
⁴⁴
Solving the above equation would yield us with the rate as 9.75% ≈ 9.8% (rounded off to tenth place after decimal)
Hence the Interest rate required by John would be 9.8%
