Question

Lashonda purchased a prepaid phone card for $20. Long distance calls cost 12 cents a minute using this card. Lashonda used her card only once to make a long distance call. If the remaining credit on her card is $17, how many minutes did her call last?

Answer 1

Given that the long distance calls cost 12 cents (i.e. $0.12) per minute.

Let Lashonda spent 'x' minutes on the call,

Then the associated cost is given by,

$\begin{gathered} C=\text{Cost per minute}\times\text{ No. of minutes} \\ C=0.12\times x \\ C=0.12x \end{gathered}$

Given that the total cost initially was $20, and the cost remaining after making the call is $17,

$\begin{gathered} \text{Total Cost=Cost Spent on Call+Remaining Cost on Card} \\ 20=0.12x+17 \\ 0.12x=20-17 \\ 0.12x=3 \\ x=\frac{3}{0.12} \\ x=25 \end{gathered}$

Thus, her call lasted for 25 minutes.