Understanding Interest Practice

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Question
Determine whether an 8.3% simple interest rate or a 7.2% compound interest rate with interest compounded monthly is the better investing option when $3,800 is invested for 4 years.

Enter 1 if an 8.3% simple interest rate is the better option.

Enter 2 if a 7.2% compound interest rate with interest compounded monthly is the better option.

(1 point)
Remaining Attempts : 3

1 answer

To determine which is the better investment option, we will calculate the future value for both the simple interest and the compound interest scenarios.

Option 1: Simple Interest

The formula for simple interest is: \[ A = P(1 + rt) \] Where:

  • \( A \) = the total amount of money after interest
  • \( P \) = principal amount (initial investment)
  • \( r \) = annual interest rate (as a decimal)
  • \( t \) = time in years

For the simple interest:

  • \( P = 3,800 \)
  • \( r = 8.3% = 0.083 \)
  • \( t = 4 \)

Calculating: \[ A = 3,800(1 + (0.083)(4)) \] \[ A = 3,800(1 + 0.332) \] \[ A = 3,800(1.332) \] \[ A \approx 5,063.60 \]

Option 2: Compound Interest

The formula for compound interest is: \[ A = P\left(1 + \frac{r}{n}\right)^{nt} \] Where:

  • \( A \) = the total amount of money after interest
  • \( P \) = principal amount (initial investment)
  • \( r \) = annual interest rate (as a decimal)
  • \( n \) = number of times interest is compounded per year
  • \( t \) = time in years

For the compound interest:

  • \( P = 3,800 \)
  • \( r = 7.2% = 0.072 \)
  • \( n = 12 \) (compounded monthly)
  • \( t = 4 \)

Calculating: \[ A = 3,800\left(1 + \frac{0.072}{12}\right)^{12 \cdot 4} \] \[ A = 3,800\left(1 + 0.006\right)^{48} \] \[ A = 3,800\left(1.006\right)^{48} \] \[ A \approx 3,800 \times 1.34885 \] \[ A \approx 5,120.43 \]

Conclusion

  • Future value with simple interest: $5,063.60
  • Future value with compound interest: $5,120.43

Since $5,120.43 (compound interest) is greater than $5,063.60 (simple interest), the better option is: Enter 2 (7.2% compound interest rate compounded monthly).