Question 29517
Hello, I can help you!
I will solve this problem by working backwards meaning i will start with the total of $4 and work down.
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First you should:
subtract .50 from $4 for the 1st minute of the call. 
{{{4.00-.50=3.50}}}
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Next step: divide 3.50 by .15 
{{{3.50/.15=23.33}}}
<i><u>round 23.33 minutes to 23 minutes</i></u>
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Now we have 23 minutes at .15(15 cents) and 1 minute at .50(50 cents):
{{{23+1=24}}}
<p> Mark and his sister can talk for 24 minutes. 
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to find out how much he will get charged simply plug in the numbers:
{{{1 min(.50)+ 23 min(.15)}}} 
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Multiply: Now you have
{{{.50+3.45=3.95}}}
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So Mark will be Charged $3.95.
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If you have any questions e-mail me at Southqueensb@yahoo.com
~EVY~