Math question. What do I need to get an A?

Question

If I have 3 tests that make up my grade in a class, and an A is between 90% and 100%. What do I need on my last test to get the A?
1st test -90%
2nd test- 84%

And please tell me how you figured it out!
Thanks!

Answer 1

Given the results of the two tests are 90% and 84%, we are interested to have a result in the third test such that the average of these three (3) tests will fall under the range of A. That is:

Let x be the result of the third test in percentage. So we have,
AVERAGE = (90% + 84% + x) / 3.

Since A lies within the range of 90% to 100%, we want the average to lie on this range. That is,
90% <= AVERAGE <= 100%.

Case 1: 90% <= AVERAGE

If the target grade is the lower bound of A, that is 90%, then we have the following:
90% <= (90% + 84% + x%) / 3
270% <= 90% + 84% + x
x <= 270% - 90% - 84%
x <= 96%.

Thus, you have to obtain a score of at least 96% to get a grade of A in the class.

Case 2: AVERAGE <= 100

If the target grade is the upper bound of A, that is 100%, then we have the following:
100% <= (90% + 84% + x%) / 3
300% <= 90% + 84% + x
x <= 300% - 90% - 84%
x <= 126%.

Thus, you have to obtain a score of at most 126% to get a grade of A in the class.

Combining these two results, we have 96% <= x <= 126%. That means, your score in the third test must ranged from 96% to 126% to obtain a grade of A in the class.

Note that in some instances that a student's grade in a test can exceed 100% whenever the student answered correctly the bonus item(s) (commonly a very tough item) given by the teacher (or professor) in a test.

Answer 2

at least 96.
at least a 90 is needed for an A. you already got 90 for the first one. You're 2nd one is 6 points short of getting an A. your last one has to be 90 + 6 to make up for the 2nd one. so 96.

Mathematically, it will look like this.
1. (90 + 84 + C) / 3 = 90
2. (174 + C) = 90 x 3
3. 174 + C = 270
4. C = 270 - 174
5. C = 96

Answer 3

Let X = third test grade

(90 + 84 +x) / 3 > 90%

solve for X:

90 + 84 + X > 270

X > 270 - 90 - 84

X > 96

meaning that you have to get at least a 96% on the third test!

Answer 4

90 average means 270 total on 3 tests.
you have 90+84=174 so far.
You need 270-174=96 on the last test.

If this is for your math class, i think you have a problem.

Answer 5

90+84+96=270

270/3=90%
u need to get approximately 96% on ur last test in order to get an A.

good luck

Answer 6

you already have one ninety so you need another on the next test plus 6 points to make up for the 84 you got on the other test.
if they are all weighted the same.

Answer 7

u need a 96% to get at least a 90% (A)

Answer 8

You need at least a 96

Answer 9

At least 96.

Answer 10

atleast 96....if all the three exams have same weightage..