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Discounts. We use the following formulas to solve the problems involving
discounts:
π«πππππππ ππππππ
= ππππππππ ππππ(πππππππ ππ π πππππππ) β ππππππππ πππππ
πΊππππ πππππ = πΆππππππ πππππ β π«πππππππ ππππππ.

Example 9. A dictionary that normally sells for \$16.50 is on sale at 40% off.
a. What is the amount of discount? Answer:\$6.60
b. What is the dictionaryβs sale price? Answer: \$9.90
Note. To find the sale price, you can also do the following:
ππππ πππππ = 0.6 β 16.50 = \$9.90, (why?).
β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦β¦.
The Percent of Decrease and Percent of Increase. To find the percent of
decrease we use the following formulas,
π·ππππππ ππ π«πππππππ =

ππππππ ππ ππππππππ
,
ππππππππ ππππππ

π·ππππππ ππ π°πππππππ =

ππππππ ππ ππππππππ
.
ππππππππ ππππππ

Note. In finding the percent of decrease, the original number is the larger
number, and in finding the percent of increase, the original number is the smaller
number.

Example 10. A FAX machine regularly sells for \$380. The sale price is \$266. Find
the percent decrease (the discount rate).
Solution. π΄πππ’ππ‘ ππ πππππππ π = 380 β 266 = \$114,
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