You decide you want to buy a house in 5 years and need to have a down payment of $75,000. A high yield money market account has an annual interest rate of 7 percent. Which calculation would you use to determine if a monthly deposit of $300.00 would be enough to reach your goal?

1 answer

To determine if a monthly deposit of $300.00 would be enough to reach your goal of having a down payment of $75,000 in 5 years, you can use the future value of an ordinary annuity formula.

The future value \( FV \) of an ordinary annuity can be calculated using the following formula:

\[ FV = P \times \frac{(1 + r)^n - 1}{r} \]

Where:

  • \( FV \) = future value of the annuity (the amount you want to have after 5 years, which is $75,000)
  • \( P \) = monthly deposit (which is $300)
  • \( r \) = monthly interest rate (annual interest rate divided by 12)
  • \( n \) = total number of deposits (number of years multiplied by 12)

Given that the annual interest rate is 7%, the monthly interest rate \( r \) would be:

\[ r = \frac{0.07}{12} \approx 0.00583333 \]

The total number of deposits over 5 years would be:

\[ n = 5 \times 12 = 60 \]

Now, you would substitute the values into the future value formula to see if the result equals or exceeds $75,000:

\[ FV = 300 \times \frac{(1 + 0.00583333)^{60} - 1}{0.00583333} \]

After calculating this result, if \( FV \) is equal to or greater than $75,000, then the monthly deposit of $300 is sufficient. If it's less than $75,000, you may need to increase your monthly deposit or find ways to earn a higher interest rate.

Therefore, the calculation you would use is the future value of an ordinary annuity formula as specified above.