Mary purchased a prepaid phone card for $30 . Long distance calls cost 24 cents a minute using this card. Mary used her card only once to make a long distance call. If the remaining credit on her card is $21.60 , how many minutes did her call last?

Respuesta :

Since .24 times 9 is 2.16, then she spent 9 minutes on the phone.

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35 minutes just keep subtracting .24 from $30 until you get the total amount of $21.60