SOLUTION: 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

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Question 187797: 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!

Found 2 solutions by Earlsdon, Edwin McCravy:
Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
Ok, you're headed in the right direction:
80%3C=%2868%2B82%2B87%2B89%2Bx%29%2F5%29%3C90 First, multiply all three elements by 5.
400%3C=%2868%2B82%2B87%2B89%2Bx%29%3C450 Now add the integers in the middle.
400%3C=326%2Bx%3C450 Now subtract 326 from all three elements.
highlight%2874%3C=x%3C124%29

Answer by Edwin McCravy(20054) About Me  (Show Source):
You can put this solution on YOUR website!
Edwin's solution:
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!

What you need is this three sided inequality:

80+%3C=+%2868%2B82%2B87%2B89%2Bx%29%2F5+%3C+90

80+%3C=+%28326%2Bx%29%2F5+%3C+90

Multiply all three sides by 5

5%2880%29+%3C=+5%28%28326%2Bx%29%2F5%29+%3C+5%2890%29

400+%3C=+326%2Bx+%3C+450%29

Subtract 326 from all three sides:

74+%3C=+x+%3C+124

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

74+%3C=+x+%3C=+100

Edwin