Question

Ronald is trying to reconstruct his spending pattern from May. He knows that he had $315 in his account on May 1, but after that, his receipts and balance statements are all scrambled. Here are Ronald’s records:

Date
Transaction Type
Amount ($)
5/25
Purchase
66
5/18
Purchase
90
5/30
Purchase
188
5/24
Deposit
151
5/22
Purchase
152
5/8
Deposit
104
5/3
Purchase
175
5/6
Purchase
82

Assuming that this is a complete, if scrambled, record of Ronald’s May spending and that any overdraft fees incurred do not affect the running total, how many times did Ronald overdraw his account in May?
a.
Ronald never overdrew his account.
b.
Ronald only overdrew his account once.
c.
Ronald overdrew his account twice.
d.
Ronald overdrew his account more than twice.

Answer 1

Order the transactions by date and keep a running balance (start $315):

- 5/3 purchase 175 → 315 − 175 = 140
- 5/6 purchase 82 → 140 − 82 = 58
- 5/8 deposit 104 → 58 + 104 = 162
- 5/18 purchase 90 → 162 − 90 = 72
- 5/22 purchase 152 → 72 − 152 = −80 (first overdraft)
- 5/24 deposit 151 → −80 + 151 = 71
- 5/25 purchase 66 → 71 − 66 = 5
- 5/30 purchase 188 → 5 − 188 = −183 (second overdraft)

He overdraws twice. Answer: c.