Name
Date
Class
Practice B
LESSON
8-1
Variation Functions
Write and graph each function.
1. y varies directly as x, and
y ⫽ 30 when x ⫽ ⫺6.
2. y varies inversely as x, and
y ⫽ 5 when x ⫽ 3.
15
y ⫽ ___
x
y ⫽ ⫺5x
Y
X
Y
X
Determine whether each data set represents a direction variation, an
inverse variation, or neither.
3.
x
8
12
16
y
2
3
4
4.
y __
1
In each case, __
x ⫽ 4 ; the ratio
is constant, so this represents a
direct variation.
x
3
1
0.5
y
5
15
30
In each case, xy ⫽ 15; the product is constant, so this represents
an inverse variation.
Solve.
5. The number of chaperones, c, needed for the class trip varies directly as
the number of students, s, going on the trip, and c ⫽ 7 when s ⫽ 56. How
many chaperones are needed if 104 students go on the class trip?
13 chaperones
6. The owner of a bookstore developed a model for determining the price of
rare comic books. The price, P, of each book should vary directly with the
number of people, N, that have requested the book and inversely to the
number of such books in existence, M. If N ⫽ 10 people, M ⫽ 10,000 copies
and P ⫽ $5, then find P for N ⫽ 200 people and M ⫽ 100 copies.
$10,000
Copyright © by Holt, Rinehart and Winston.
All rights reserved.
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