Chapter 9 linear inequaliTieS 325- A company providing cell phone service has two plans. The monthly
charge on one plan is $75 with unlimited talk and Web access. The
monthly charge for the other plan is $15 plus 20 cents per minute of
talk and web access. How much time per month would a customer
need to use the phone for talk and web access so that the unlimited
plan is less expensive than the other plan? - Sharon can purchase a pair of ice skates for $60. It costs her $3 to rent a pair
each time she goes to the rink. How many times would she need to use the
skates to make purchasing them more attractive than buying them? - The James family has $210 budgeted each month for electricity. They have
a monthly base charge of $28 plus 7 cents per kilowatt-hour. How many
kilowatt-hours can they use each month to stay within their budget? - A warehouse store charges an annual fee of $40 to shop there. A shop-
per without paying this fee can still shop there if he pays a 5% buyer’s
premium on his purchases. How much would a shopper need to spend
at the store to make paying the annual $40 fee cost no more than pay-
ing the 5% buyer’s premium? - A sales clerk at an electronics store is given the option for her salary to
be changed from a straight annual salary of $25,000 to an annual base
salary of $15,000 plus an 8% commission on sales. What would her
annual sales level need to be in order for this option to be at least as
attractive as the straight salary option?
✔SOLUTIONS
- Let x = amount invested in the corporate bond
500,000 – x = amount invested in the treasury bond
0.08x = annual interest from the corporate bond
0.0525(500,000 – x) = annual interest from the treasury bond
Corporate bond interest + Treasury bond interest ≥ 30,000
0080 0525 500 000 30 000
00826. .(, ) ,
. ,
xx
x+ – ≥
+ 2250 0 0525 30 000
26 250 26 250
0 0275 . ,
,–,
.
– ≥ ≥ xx- 33750
3750
0 0275
136 363 64
x
x.
,.≥
≥