Question 187797
<font size = 8 color = "red"><b>Edwin's solution:</b></font>

hi, i have a lot of trouble with word problems and was wondering if you could help. here is the problem.

In your economics 101 class, you have scores of 68, 82, 87 and 89 on the first four of five tests. To get a grade of B, the average of the first five test scores must be greater than or equal to 80 and less than 90. Solve an inequality to find the range of the score that you need on the last test to get a B. 

i did (68+82+87+89+x)/5 > 80 but I dont think that really helps.

thank you!
<pre><font size = 4  color = "indigo"><b>
What you need is this three sided inequality:

{{{80 <= (68+82+87+89+x)/5 < 90}}}

{{{80 <= (326+x)/5 < 90}}}

Multiply all three sides by {{{5}}}

{{{5(80) <= 5((326+x)/5) < 5(90)}}}

{{{400 <= 326+x < 450)}}}

Subtract 326 from all three sides:

{{{74 <= x < 124}}}

Since it is impossible to make over 100
we must chop the right end-value down
to 100. So the answer is:

{{{74 <= x <= 100}}}

Edwin</pre>