Question

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.

Answer 1

Answer: 1) 300 min

2) 680 min

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