Stock Trading and Other Things

An example of a math problem that stock brokers need to do?

i need to do a project for my math class about what kind of math problems stock brokers do. I really really need an example because i have no idea what they do
HELP!

Public Comments

1. Account value: $10,000
Margin Interest rate: 7.95% APR
Transaction: $20,000 of XYZ purchased on 1/01 and sold on 1/15

1. Take the amount of money borrowed and multiply it by the interest rate:
10,000 * .0795 = 795
2. Take the product and divide it by the number of days in the year:
795 / 360 = 2.21
3. Multiply this result by the number of days XYZ was held on margin:
2.21 * 15 = 33.15

It would cost $33.15 to borrow $10,000 for 15 days.