Percent of Change / Commission / Sales Tax

At the bottom of this page you will find a section for making practice problems along with the answers. Additionally worksheets and answer keys can also be generated and printed.

TERMS AND FORMULAS YOU NEED TO KNOW
These are all "percent of problems". Commission is a percent of the sales, sales tax is a percent on the amount of the purchase, percent increase and percent decrease are both percents of the original or starting amount.

Commission / Earnings
1. Commission (C) -- the amount of money a person is paid based on their sales.
2. Commission percent (C%) -- the commission percent.
3. Sales (S) -- the amount of sales the commission is paid on.
4. Earnings is the sum of someone's regular pay (P) and their commission.

5. C = C%•S    ----     Commission = Commission% • Sales
6. E = P + C     ----     Earnings = Regular Pay + Commission

Sales Tax / Total Cost
1. Tax percent (T%) -- the tax percent or tax rate paid on a purchase.
2. Tax (T) -- the amount of money payed in tax on a purchase.
3. Purchase (P) -- the amount of money payed for a purchase.
4. Total cost (TC) -- the sum of the purchase price and the sales tax.

5. T = T% • P     ----     Tax = Tax% • Amount of Purchase.
6. TC = P + T     ----     Total Cost = Price + Tax.

Percent of Increase / Percent of Decrease
1. Change percent (C%) -- the percent of the change.
2. Chang amount (C) -- the amount of the change, up or down, positive or negative.
3. Starting amount, initial amount, beginning amount (S) -- the amount at the beginning or start.
4. Ending amount, final amount (E) -- the amount at the end or when the change is finished.

5. C = E - S     ----     amount of change = ending amount - starting amount.
6. C% = C ÷ S     ----     percent of change = change ÷ starting amount.
7. C% = (E - S) ÷ S     ----     another formula for the percent of change.

Problem # 1