2-9 Per cen t s
Quick Review Ex e r c i se s
A percent is a ratio th at com pares a n u m b e r to 100. If you 52. W hat p ercen t of 37 is 111?
write a percent as a fraction, you can use a p ro p o rtio n to
solve a p ercent problem. 53. W hat is 72% of 150?- 60% of w hat n u m b e r is 102?
Ex a m p l e 55. Gardening A gardener expects th at 75% of the seeds
What percent of 84 is 105? she plants will produce plants. She w ants 45 plants.
W = lho ^r'te Percent proportion. How m any seeds should she plant?
100(105) = 84p Cross Products Property 56. Fundraising A charity sent out 700 fundraising
10,500 = 84p Simplify. letters a n d received^210 contributions in response.
W hat was th e p ercen t of response?
125 = p Divide each side by 84.
105 is 125% of 84. - Surveys In a survey, 60% of stu d en ts prefer bagels
to donuts. If 120 students were surveyed, how m any
stu d en ts prefer bagels?
2-10 Ch an g e Ex p r essed a s a Per cen t
/ ^^— ^Ex e r c i se s
Tell whether each percent change is an increase or
decrease. Then find the percent change. Round to the
nearest percent.- original am ount: 27 59. original am ount: 250
new a m o u n t: 30 new a m o u n t: 200 - original am ount: 873 61. original am ount: 4.7
new am ount: 781 new am ount: 6.2 - Demographics In 1970, the U.S. p o pulation was
ab o u t 205 m illion people. In 2007, it was about
301 million. W hat was th e p ercen t increase? - Astronom y The tim e from sunrise to su n set on the
shortest day of th e year in Jacksonville, Florida, is
ab o u t 10 h 11 m in. On the longest day, the tim e is
14 h 7 m in. W hat is th e p ercen t increase? - W eather This m orning th e tem p eratu re was 38°F.
This afternoon it is 57°F. Did th e tem p eratu re
increase by 50%? Explain.
Quick Review
Percent change p% is th e ratio of the a m o u n t of change to
the original am ount.
^ _ amount of increase or decrease
” 0 original amount
You can use the p ercent change form ula to express changes
as percents.Ex a m p l e
A bookstore buys a book for $16 an d m arks it up to $28.
W hat is th e m arkup expressed as a p ercen t change?
, new amount — original amount
p ercen t change = Original amount---------= ^8 1616 Substitute.= yg^12 Simplify.
= 0.75 or 75% Write the result as a percent.
The price of th e book increased by 75%.156 Ch ap t er 2 So l v i n g Eq u a t i o n s