Percent of change (increase or decrease)
Scales
Discounts, mark-ups
Commissions
Checking account
Writing checks
Balancing checkbook
Interest
Simple
Compound
Taxes

Percent of change (increase or decrease)
Scales
Discounts, mark-ups
Commissions
Checking account
Writing checks
Balancing checkbook
Interest
Simple
Compound
Taxes

Percent of Increase and Decrease
To find the percent of change, first find the difference between the new value and the original value. Then, place the number obtained over the original value
and use this fraction as the first half of a proportion with n over 100 as the second half. Solve for n to give the percent of change.
Simple Interest
To calculate simple interest use the following formula: I = p x r x t
I = interest is always entered as $ amount, p = principal� (amount invested or borrowed), r = rate of percent is always entered as a %, t = time (if not in even
years) is converted to a fraction (six months = 6/12), then� to a decimal. (.5).
Commission
Commission is a percent of sales. To find a commission, multiply the sales by the commission rate. Some professions receive a salary as well as a
commission. To find total income, just add the commission to the salary.
Discounts and Sale Price
A discount is a percentage of decrease in regular price. The sale price is the total cost of an item after the discount is taken.
Sale Price = Original Price - Discount
To find the discount change the percentage to a decimal and then multiply. Money always rounds to 2 decimal places (the nearest hundredths).