a celluar phone company offers a contract which the cost c, in dollars, of t minutes of telephoning is given by c=0.25(t-600) plus 57.95 where it is assumed that t is > or eqaul to 600 minutes. what time will keep cost below 102.45 and 135.20?
Assuming that your equation is correct:
102.45 ≥ 57.95 + .25(t-600)
Solve for t.
Do the same for $135.20.
To find the time (t) that will keep the cost below $102.45 and $135.20, we can use the given formula:
c = 0.25(t - 600) + 57.95
For cost below $102.45:
Substitute c with $102.45 in the equation and solve for t:
102.45 = 0.25(t - 600) + 57.95
44.5 = 0.25(t - 600)
44.5/0.25 = t - 600
178 = t - 600
t = 178 + 600
t = 778
Therefore, to keep the cost below $102.45, you can use the phone for up to 778 minutes.
For cost below $135.20:
Substitute c with $135.20 in the equation and solve for t:
135.20 = 0.25(t - 600) + 57.95
77.25 = 0.25(t - 600)
77.25/0.25 = t - 600
309 = t - 600
t = 309 + 600
t = 909
Therefore, to keep the cost below $135.20, you can use the phone for up to 909 minutes.