6. a cell phone company offers a contract for which the cost C, in dollars, of t minutes of telephoning?

Question

is given by C=0.25(t-400)+47.95, where it is assumed that t>=400 minutes. What times will keep costs between $86.20 and $114.95?

23. solve and grapgh the compound inequity

2x-14<=-7 or x-6>=1

the solution of the compound inequality is {x|x<=__ or x>=__}?.

Jun Agruda · Accepted Answer

0.25(t - 400) + 47.95 = 86.20
0.25(t - 400) = 38.25
t - 400 = 153
t = 553

0.25(t - 400) + 47.95 = 114.95
0.25(t - 400) = 67
t - 400 = 268
t = 668

Answer: 553 ≤ t ≤ 668 or Between 553 and 668
-----------
2x - 14 ≤ - 7
2x ≤ 7
x ≤ 7/2 or 7/2 ≥ x

x - 6 ≥ 1
x ≥ 7 

Answer: 7/2 ≥ x ≥ 7???????

peabody · Answer

C=0.25(t-400)+47.95

86.20 = 0.25(t-400)+47.95

(86.20 - 47.95)/.25 = t - 400

t = (86.20 - 47.95)/.25 + 400

= 553 mins

114.95 = 0.25(t-400)+47.95

(114.95 - 47.95)/.25 = t -400

t = (114.95 - 47.95)/.25 + 400

= 668 mins

23) 2x -14 <= -7

2x<= -7 +14

2x <- 7

x <- 7/2

x -6 >= 1

x >= 7

{x|x<= -7/2 or x>= 7}

Graph the compound inequality gives two regions to the left an equal to -7/2 and to the right or equal

to 7.

mathgeek · Answer

For the first one, just set C = to the wanted costs:

86.20 = 0.25(t-400)+47.95 and 114.95 = 0.25(t-400)+47.95

and solve for t. Give the answer like this: (minutes for first part) <= t <= (minutes for last part). I'll let you put it in the calculator!

For the second one,

2x - 14 <= -7

2x <= -21

x<= -21/2

x- 6 >= 1

x >= 7

Therefore, {x|x<= -21/2 or x>= 7}

6. a cell phone company offers a contract for which the cost C, in dollars, of t minutes of telephoning?

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