Last month a phone company charged $ 0.07 per minute for the first 300 minutes of calling time and $0.05 per minute for each minute of calling time in excess of the first 300 minutes. For how many minutes of calling time was Bob charged by the phone company last month?1) Last month the phone company charged Bob $21.00 for his calling time that was charged at $0.07 per minute. 2) Last month the phone company charged Bob $40.00 for his calling time that was charged at $0.05 per minute.

Question

Mathematics

Clara Buck

19 December, 06:14

Last month a phone company charged $ 0.07 per minute for the first 300 minutes of calling time and $0.05 per minute for each minute of calling time in excess of the first 300 minutes. For how many minutes of calling time was Bob charged by the phone company last month?1) Last month the phone company charged Bob $21.00 for his calling time that was charged at $0.07 per minute. 2) Last month the phone company charged Bob $40.00 for his calling time that was charged at $0.05 per minute.

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Odin Page · Answer 1

Answer: 1) 300 min

2) 680 min

Step-by-step explanation:

1) As the charge was $21 at 0.07, x is the minutes he used, we have:

0.07x = 21

x = 21/0.07

x = 300

2) As the charge was $40 and the company charges different rates for minutes, we know from 1 that the first 300 min costs $21, we have

40 - 21 = 19

So $19 was charged with the $0.05 fee. so:

0.05x = 19

x = 19/0.05

x = 380

300 + 380 = 680 min