College

Select the correct answer.

Each month, Barry makes three transactions in his checking account:

- He deposits [tex]$\$ 700$[/tex] from his paycheck.
- He withdraws [tex]$\$ 150$[/tex] to buy gas for his car.
- He withdraws [tex]$\$ 400$[/tex] for other expenses.

If his account balance is [tex]$\$ 1,900$[/tex] at the end of the 1st month, which recursive equation models Barry's account balance at the end of month [tex]$n$[/tex]?

A. [tex]$f(1) = 1,900$[/tex]
[tex]$f(n) = f(n-1) + 150$[/tex], for [tex]$n \geq 2$[/tex]

B. [tex]$f(1) = 1,900$[/tex]
[tex]$f(n) = 150 \cdot f(n-1)$[/tex], for [tex]$n \geq 2$[/tex]

C. [tex]$f(1) = 1,900$[/tex]
[tex]$f(n) = f(n-1) + 700$[/tex], for [tex]$n \geq 2$[/tex]

D. [tex]$f(1) = 1,900$[/tex]
[tex]$f(n) = f(n-1) - 150$[/tex], for [tex]$n \geq 2$[/tex]

Answer :

To solve this problem, let's examine Barry's monthly transactions:

1. Barry deposits [tex]$700 from his paycheck into his account each month.
2. He withdraws $[/tex]150 to buy gas.
3. He withdraws [tex]$400 for other expenses.

To find the net change to his account each month, we calculate the difference between the deposits and withdrawals:

- Total deposit: $[/tex]700
- Total withdrawals: [tex]$150 (for gas) + $[/tex]400 (for other expenses) = [tex]$550

The net change to his account balance each month is:

\[ \text{Net change} = \text{Total deposit} - \text{Total withdrawals} \]

\[ \text{Net change} = 700 - 550 = 150 \]

This tells us that Barry's account balance will increase by $[/tex]150 each month after all transactions.

Given that the account balance at the end of the 1st month is $1,900, we can use this information to model the recursive equation for his account balance at the end of month [tex]\( n \)[/tex]:

- Start with the balance at the end of the 1st month: [tex]\( f(1) = 1,900 \)[/tex]
- For each subsequent month, use the recursive relationship:
[tex]\[ f(n) = f(n-1) + 150 \][/tex]
where [tex]\( n \geq 2 \)[/tex].

The correct recursive model for Barry's account balance is:

- [tex]\[ f(1) = 1,900 \][/tex]
- [tex]\[ f(n) = f(n-1) + 150 \][/tex], for [tex]\( n \geq 2 \)[/tex].

Therefore, the correct answer is option A.