Math Problem Statement

Your grandmother has been putting $ 2 comma 000 into a savings account on every birthday since your first​ (that is, when you turned​ one). The account pays an interest rate of 7 %. How much money will be in the account immediately after your grandmother makes the deposit on your 18th birthday

Solution

To solve this problem, we can use the formula for the future value of a series of cash flows (or annuity), since your grandmother makes a deposit every year and the account earns interest.

The formula for the future value FVFV of an annuity is:

FV=P×(1+r)n1rFV = P \times \frac{(1 + r)^n - 1}{r}

Where:

  • PP is the annual deposit (in this case, $2,000),
  • rr is the annual interest rate (in this case, 7% or 0.07),
  • nn is the number of deposits (in this case, 18 since there are deposits starting from your first birthday through your 18th birthday).

Step-by-Step Calculation:

  1. Annual deposit PP = $2,000.
  2. Annual interest rate rr = 7% = 0.07.
  3. Number of deposits nn = 18.

Let's calculate this.The amount of money in the account immediately after your grandmother makes the deposit on your 18th birthday will be approximately $67,998.07.

Would you like more details on any part of the calculation? Here are 5 related questions for further exploration:

  1. What would the balance be if the interest rate were lower, say 5%?
  2. How much interest has been earned by the 18th birthday?
  3. How would the final amount change if the deposits were made at the end of each year instead?
  4. What would be the future value if deposits were made for 25 years instead of 18?
  5. How would monthly deposits of $200 instead of yearly deposits affect the total?

Tip: The earlier you start saving or investing, the more you benefit from compound interest over time.

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Math Problem Analysis

Mathematical Concepts

Compound Interest
Future Value of Annuity
Series of Cash Flows

Formulas

Future Value of Annuity: FV = P × [(1 + r)^n - 1] / r

Theorems

Compound Interest Formula

Suitable Grade Level

Grades 10-12