On Roy's first birthday, his grandfather placed $100 in a bank account. On Roy's second birthday, his grandfather placed $80 in the account and continued to place $80 each passing year. The arithmetic sequence 100, 180, 260, 340,… indicates the account balance for the first four years. Create a function that models this situation.

Answer 1

The function that models this situation is:

f(n) = 80n + 20

where n represents Roy's age in years.

Generally, n = 1 will represent Roy's 1st birthday, n = 2 for his 2nd birthday, and so on.

Thus:
- f(1) = 80(1) + 20 = 100
- f(2) = 80(2) + 20 = 180
- f(3) = 80(3) + 20 = 260
- f(4) = 80(4) + 20 = 340