Question

Calls from a call box are charged per minute at one rate for the five minutes, then a different rate for each additional minute. If a 7-minute call costs $4.25 and a 12-minute call costs $5.50, find each rate.​

a.$ 1.50 per minute at one rate for the first 5 minutes and $0.50 per minute thereafter
b.$3.20 per minute at one rate for the first 5 minutes and $0.55 per minute thereafter
c.$0.75 per minute at one rate for the first 5 minutes and $0.25 per minute thereafter
d.$2.40 per minute at one rate for the first 5 minutes and $0.75 per minute thereafter
Which answer is it ?????????

Answer 1

c. $0.75 per minute at one rate for the first 5 minutes and $0.25 per minute thereafter

Explanation:

The last 5 minutes of the 12-minute call cost ...

$5.50 -4.25 = $1.25

so the per-minute rate at that time is ...

$1.25/(5 min) = $0.25/min . . . . . . . . matches choice C only

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You know the answer at this point, but if you want to check the rate for the first 5 minutes, you can subtract 2 minutes from the 7-minute call to find that ...

The first 5 minutes cost $4.25 - 2·0.25 = $3.75, so are charged at ...

$3.75/(5 min) = $0.75/min . . . . . . . matches choice C