Math
posted by Katherine .
In Wilbur's math class, his grade is based on the average score of six tests, each worth 100 points. Wilbur always worries about his grade. He knows that his average on the four first tests is 88.5. What is the lowest average he could get on his next two tests and still average 90 overall...
please help me i am very confused.....
i need the formula

4 * 88.5 = 354 Total points so far
600 * 0.9 = 540 Total possible for 6 tests
540  354 = 186
186/2 = 91 average on the next two tests 
can i get the formula...please
this is what i got.....
the formula is (88.5 + x + y) divide 3=90
90 * 3 =270
so then (88.5 + 91.5 + 90)=270 /3=90
90*3=270 
I don't understand your formula. But you didn't get an answer for your problem.

But the total average has to be 90 not 91 . So we are right , right ?

The total average must be 90. But Wilbur only has 88.5 average at this point. His average grade on the next two tests must be more than 90 for his overall average to be 90.

no it doesnt . Because if you add 88.5+90+91.5 you get 270 and then you divide 3 you get 90.

I'm sorry you didn't understand my explanation. I averaged grades for 32 years in my teaching career and should know what I'm talking about. You cannot bring up an 88.5 average to 90 with only a couple of 90 test scores.
Please sit down with your teacher to have him/her explain this problem to you. 
Ok i don't understand your formula either. Im sorry, but thankyou anyways. OKAY !!!!

Use The following equation:n 2x+4(88.5)/(6)=90. Solve for x.
x=93 
IDK

Why multiple by 0.9???

I got 94
Im a bad teacher 
You multiply by .9 since that in percentage is 90%. He wants a total average of 90% for his remaining tests. The answer is 91.

I got 93