Marie scored 95, 86, and 89 on three science tests. She wants her average score for 6 tests to be at least 90. What inequality can you write to find the average scores that she get on her next three can tests to meet this goal?

1 Answer
Nov 10, 2016

The inequality that needs to be solved is: #(3t + 270)/6 >= 90#.

She needs to average at least 90 on her three remaining tests to have at least a 90 overall average for all 6 tests.


To obtain an average you first add up all the scores of the tests and then divide by the number of tests.

So far Marie has taken 3 tests and we know the total number of tests will be 6 so we will be dividing by 6 to get the average of all the score.

If we let each of the three remaining tests each be represent by #t# then the sum of all the tests would be:

#95 + 86 + 89 + t + t + t#


#270 + 3t#

The average of these 6 tests can then be represented by:

#(3t + 270)/6#

And for her average to be at least 90 then she can get a 90 or more which is the same as #>= 90#

So the inequality that needs to be solved is:

#(3t + 270)/6 >= 90#


#t/2 + 45 >= 90#

#t/2 >= 45#

#t >= 90#