Does this problem
involve a percent
decrease or a percent
increase?
The n e w a m o u n t is less
than the original amount,
so the problem involves a
percent decrease.
A co m m o n exam ple of finding a p ercen t d ecrease is finding a p ercen t discount. In this
lesson, ro u n d your answ ers to th e n ea rest percent, if necessary.Problem 1 Finding a Percent Decrease
Clothing A coat is on sale. The original price of the coat is $82. The sale price is
$74.50. What is the discount expressed as a percent change?percent change. amount of increase or decrease original amount
original amount — new amount
original amount. 8 2 - 7 4. 5 0
82
725
82
5=5 0.09, or 9%
The price of th e coat d ecreased by ab o u t 9%.This is a p e rc e n t decrease. W rite
the a p propriate ratio.
Substitute.Simplify.Write the result as a percent.G o t It? 1. The average m o nthly precipitation for Chicago, Illinois, peaks in June at
4.1 in. The average m on th ly precipitation in D ecem ber is 2.8 in. W hat is
th e p ercen t d ecrease from June to D ecem ber?Have you seen a
problem like this one?
Yes. Fin d in g p e rc e n t
increase is like fin d in g
percent decrease.
The d iffe re n ce is in
calculating the amount
o f increase o r decrease.
A co m m o n exam ple of finding a p ercen t increase is finding a p ercen t markup.Problem 2 Finding a Percent Increase
Music A store buys an electric guitar for $295. The store then marks up the price of
the guitar to $340. What is the markup expressed as a percent change?p ercen t change =amount of increase or decrease
original amountnew amount — original amount340 ■original amount
295
295
= 45_
295
= 0.15 or 15%
The price of th e guitar increased by a b o u t 15%.This is a p e rc e n t incre a se. W rite
the ap p ro p ria te ratio.
Substitute.Simplify.Write the result as a percent.4 G o t It? 2. In one year, th e toll for passen g er cars to use a tu n n el rose from $3 to $3.50.
W hat was th e p e rc e n t increase?c
PowerAlgebra.com | Lesso n 2 - 1 0 Ch an g e Exp ressed as a Percen t^145