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?

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.

1) If Bob was charged $0.07 per minute, it means the call was within the first 300 minutes. He was charged $21.00 for last month at $0.07per minute. Therefore, he called for:

[tex]\frac{21.00}{0.07} = 300[/tex]

He called for 300 minutes with $21.00

2) If Bob was charged $0.05 per minute, it means the call was outside the first 300 minutes. He was charged $40.00 for last month at $0.05 per minute. Therefore, he called for:

[tex]\frac{40.00}{0.05} = 800[/tex]

He called for additional 800 minutes with $40

Therefore, the total minutes for last month is 300 + 800 = 1100 minutes.