Question

Martina purchased a prepaid phone card for $20. Long distance calls cost 24 cents a minute using this card. Martina used her card once to make a long distance call. If the remaining credit on her card is $13.28, how many minutes did her call last?

Answer 1

28 minutes
subtract 20 and 13.28, divide that answer by .24, and you get your answer

Answer 2

Find amount used:
Amount in the card = $20
Amount left = $13.28
Amount used = $20 - $13.28 = $6.72

Find duration of the call:
24 cents = 1 min
672 cents = 1/24 x 672 = 28 mins

Answer: The call was 28 minutes long.