Question

Erin has some money saved in her bank account. She adds or subtracts from the total in her

account according to the following pattern:

+1-2+3-4+5-6 + 7-8 +9

By how much will the total in her account change after nine days if she makes one transaction
per day?

Answer 1

After performing the consecutive adding and subtracting operations (+1, -2, +3, -4, +5, -6, +7, -8, +9) for nine days, the total change in Erin's bank account will be $5.

Step-by-step explanation:

Erin's pattern of saving and withdrawing money from her bank account can be broken down into a simple arithmetic problem. She follows a pattern of adding and subtracting consecutive integers starting from 1: +1, -2, +3, -4, +5, -6, +7, -8, +9. To find out the total change in her account after nine days, we simply perform these operations in sequence.

To solve this, we add all the positive numbers and subtract the sum of all the negative numbers:

• Positive numbers: 1 + 3 + 5 + 7 + 9 = 25
• Negative numbers: -2 - 4 - 6 - 8 = -20

Now, we combine these sums to find the total change: 25 - 20 = 5

Therefore, the total in Erin's account will change by $5 after nine days.