Using Percents to Solve Problems

Math 7/8

Discounts

• Find discount by multiplying percent (decimal value) by the price.

• Subtract the discount amount from the original price.

• EX) 30% discount on $450 desk .30 (450) = 135 450 – 135 = 315 The sale price is $315

Sales Tax

• Find amount of tax by multiplying the percent tax rate (decimal value) by the original price of the item.

• Add the tax amount to the original price to get the total.

• EX) $39 dress and sales tax is 6% .06 (39) = 2.34 39 + 2.34 = 41.34The cost of the dress including tax is $41.34

Tips

• Find tip by multiplying percent (decimal value) by the total.

• Add the tip amount to the final total bill.• Often times the tip is rounded to the

nearest dollar• EX) 15% tip on a bill of $26.93 .15 (26.93) = 4.04 26.93 + 4.04 = 30.97 ***round up to $31 total including tip

Simple Interest Review

• The formula for interest is: I = prtI = interestp = principle (amount of savings or loan)r = rate (decimal form)t = time in years• EX) Sarah borrowed money from the bank to

buy a car. The car was $7,800. She has to pay 4.5% interest for 36 months. How much will Sarah end up paying for her car?