13.The two domestic top-grossing movies
of 2009 were Avatarand Transformers 2:
Revenge of the Fallen.The movie Trans-
formers 2grossed $26.9 million less
than Avatar, and together the two films
took in $831.1 million. How much did
each of these movies earn? (Source:
http://www.boxofficemojo.com)
14.Two other domestic top-grossing movies
of 2009 were Upand Harry Potter and
the Half-Blood Prince. Up grossed
$8.9 million more than Harry Potter and
the Half-Blood Prince, and together the
two films took in $594.9 million. How
much did each of these movies earn?
(Source:www.boxofficemojo.com)
278 CHAPTER 4 Systems of Linear Equations and Inequalities
If x units of a product cost C dollars to manufacture and earn revenue of R dollars, the value
of x at which the expressions for C and R are equal is called the break-even quantity—the
number of units that produce 0 profit.
In Exercises 15 and 16, (a)find the break-even quantity, and (b)decide whether the product
should be produced on the basis of whether it will earn a profit. (Profit=Revenue-Cost.)
- ;
No more than 38 units can be sold.
16. ;
No more than 400 units can be sold.
C= 85 x+ 900 R= 105 x C= 105 x+ 6000 R= 255 x
19.Joyce Nemeth bought each of her seven nephews a gift, either a DVD of the movie
The Blind Sideor the latest Beyoncé CD. The DVD cost $14.95 and the CD cost $16.88,
and she spent a total of $114.30. How many of each DVD and CD did she buy?
20.Jason Williams bought each of his five nieces a gift, either a DVD of The Twilight Saga:
New Moonor the CD soundtrack to High School Musical 3: Senior Year.The DVD cost
$14.99 and the soundtrack cost $13.88, and he spent a total of $70.51. How many of each
DVD and CD did he buy?
21.Karen Walsh has twice as much money invested at 5% simple annual interest as she does
at 4%. If her yearly income from these two investments is $350, how much does she have
invested at each rate?
Number Value Total
of Coins per Coin Value
x $0.25
y $0.10
39 $7.50
Number of Total
Stamps Denomination Value
x $0.39
y $0.24
$19.44
Write a system of equations for each problem, and then solve the system. See Example 2.
17.Jonathan, a second grader, counted the
money in his piggy bank. He had only
quarters and dimes. When he added up
his money, he had 39 coins worth a total
of $7.50. How many coins of each kind
did he have?
18.Marilyn Mcintosh went to the post of-
fice to stock up on stamps. She spent
$19.44 on 56 stamps, made up of a com-
bination of 39-cent and 24-cent stamps.
How many stamps of each denomina-
tion did she buy?
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