Question

Dominic is looking over his spending pattern for the past week to try to determine how much money he had on Sunday. This is Dominic’s spending pattern:

Day
Debit ($)
Credit ($)
Monday
158
---
Tuesday
69
44
Wednesday
175
---
Thursday
131
38
Friday
---
53
Saturday
22
14

If the bank charges Dominic an overdraft fee of $25 every time he overdraws his account, and Dominic overdrew his account on Thursday but not on Saturday, which of the following is a possible amount of money that Dominic could have had in his account last Sunday? Assume that the only debits and credits not listed are overdraft fees.
a.
$500
b.
$480
c.
$435
d.
$400

Answer 1

Answer: (b) $480.

Work: Let B be the balance on Sunday. Process each day assuming a debit posts before any credit that day; whenever a debit makes the balance negative a $25 overdraft fee is immediately charged.

For B = 480:
- Mon: 480 − 158 = 322
- Tue: 322 − 69 + 44 = 297
- Wed: 297 − 175 = 122
- Thu: 122 − 131 = −9 → overdraft fee 25 ⇒ −34; then +38 ⇒ 4 (overdrew on Thursday)
- Fri: 4 + 53 = 57
- Sat: 57 − 22 = 35 (no overdraft) then +14 = 49

Thus he overdrew on Thursday but not Saturday. The other choices either do not produce a Thursday overdraft (500) or produce a Saturday overdraft (435, 400).