Question 163953
You have the formula in your head
You just can't get it out
Let {{{b}}}= Miriam's monthly bill
Let {{{t}}}= the number of text messages sent in the
month of June by Miriam
{{{t - 1000}}}= the number of text messages over {{{1000}}}
Miriam's monthly bill is:
{{{b = 10 + .1*(t - 1000)}}} dollars
Her monthly bill is $38.50. I'll show it in terms of cents
{{{3850 = 1000 + 10*(t - 1000)}}} cents
Subtract {{{1000}}} from both sides
{{{2850 = 10*(t - 1000)}}}
{{{2850 = 10t - 10000}}}
Add {{{10000}}} to both sides
{{{12850 = 10t}}}
{{{t = 1285}}} messages
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It might help to go over the units involved in the 1st
formula which was
{{{b = 10 + .1*(t - 1000)}}} dollars
The {{{10}}} really stands for ($10/1000 messages)x(1000 messages)
And the other term is really (.1 dollars/message)x(t - 1000 messages)
The units work out to dollars for both terms
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You can check the answer
{{{3850 = 1000 + 10*(t - 1000)}}}
{{{3850 = 1000 + 10*(1285 - 1000)}}}
{{{3850 = 1000 + 10*285}}}
{{{3850 = 1000 + 2850}}}
{{{3850 = 3850}}}
OK