340 algebra De mystif ieD
The manufacturing plant should produce between 10,000 and 25,000
gross per month to keep its monthly costs between $96,000 and
$150,000.
PRACTICE
- According to Hooke’s law, the force, F (in pounds), required to stretch a
certain spring x inches beyond its natural length is F = 4.2x. If 7 ≤ F ≤ 14,
what is the corresponding range for x? - The relationship between the Fahrenheit and Celsius temperature scales
is given by F = ^95 C + . 32 If 52 F≤ ≤ , 3 what is the corresponding range
for C? - A saleswoman’s salary is a combination of an annual base salary of
$15,000 plus a 10% commission on sales. What level of sales does she
need to maintain in order that her annual salary range from $40,000 to
$60,000? - The Smith’s electric bills consist of a base charge of $20 plus 12 cents
per kilowatt-hour. If the Smiths want to keep their electric bill in the
$80 to $110 range, what range of kilowatt-hours do they need to
maintain? - A particular collect call costs $2.10 plus 50 cents per minute. (The com-
pany bills in two-second intervals.) How many minutes would a call
need to last to keep a charge between $4.50 and $6.00?
✔SOLUTIONS
- 71442
74214
7
42
42
42
14
42
5
3
≤≤ =
≤≤
≤≤
≤
FFx
x
x
x
and..
.
.
.
..
≤≤^10
3
If the force is to be kept between 7 and 14 pounds, the spring will stretch
between^53 and^103 inches beyond its natural length.
PRACTICE
- According to Hooke’s law, the force,