To pass a course with a B grade, a student must have an average of 80 or greater. A student's grades on three tests are 75,83, and 86. Solve the inequality  to find what score the student must...

To pass a course with a B grade, a student must have an average of 80 or greater. A student's grades on three tests are 75,83, and 86. Solve the inequality  to find what score the student must get on the next test to get a B average or better.

 
Expert Answers
justaguide eNotes educator| Certified Educator

To pass the course with a B grade, the student must have an average of 80 or greater. It is given that on three tests the student's scores are 75,83, and 86.

Let the score that the student must get on the 4th test to get an average score of 80 or more be X.

`(75 + 83 + 86 + X)/4 >= 80`

=> `(244 + X) >= 320`

=> `X >= 76`

On the 4th test the student must get a score of at least 76.

jilltara | Student

To get a B in the course the student needs an average of 80 or greater on their tests.  To find the average score, you must total (add) all tests together, then divide by the number of tests taken.  Since we don't know what the 4th test will be, an x is used as a marker.

 

(83 + 75 + 86 + x) / 4 > 80

(244 + x) / 4 > 80

244 + x > 80 * 4

244 + x > 320

x > 320 – 244

x > 76