Karen purchased a prepaid phone card for $20 . Long distance calls cost 11 cents a minute using this card. Karen used her card only once to make a long distance call. If the remaining credit on her card is $17.47 , how many minutes did her call last?
Find what was used: Used Money = Prepaid original cost - Remaining Credit Used Money = 20 - 17.47 Used Money = 2.53 Using (m) as the number of minutes, we have the following cost equation: C(m) = 0.11m C(m) = 2.53, so we have: 0.11m = 2.53 Divide each side by 0.11 m = 23
