How many minutes can you talk if you use a $5 phone card to call a friend and the call is $.50 for the first minute and $.15 for each additional minute (or part of a minute)?

1 Answer
Shantelle
May 27, 2018

You can talk for #30# minutes.

Explanation:

First, let's list out what we know:

We have a #$5# phone card.

The first call is #$0.50#.

Every minute after that is #$0.15#.

Now, let's let #m# be the number of minutes you can talk.

We know that the minutes times the dollar amount must equal to #5#, and that #$0.50# is a constant (no matter how many minutes you call #$0.50# is still there.

Since we don't know how many minutes there are but we know the cost for every minute after, that becomes #0.15m#.

Set the equation:
#0.50 + 0.15m = 5#

Now solve for #m#. Subtract #color(blue)(0.50)# from both sides of the equation:
#0.50 + 0.15m quadcolor(blue)(-quad0.50) = 5 quadcolor(blue)(-quad0.50)#

#0.15m = 4.5#

Then divide both sides by #color(blue)0.15#:
#(0.15m)/color(blue)0.15 = 4.5/color(blue)0.15#

Therefore,
#m = 30#.

You can talk for #30# minutes.

Hope this helps!

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