Algebra 2 Question

Question

On the first 4 quizzes of her history class, Emily got an average score of 82. What does she need on the next quiz to have an overall average of 84?

Answer 1

4 quizzes, average 82.

to pull it up to 84 average

she needs to get Q where 84= (4(82)+Q)/5

5(84) = 4(82) +Q

Q = 5(84)-4(82) = 420-328 = 92 for the 5th Quiz

check the answer:

4(82)+92 = 328+92= 420

420/5 = 84 average

Answer 2

To find an average, you add together all the scores you have and divide by the number of tests. Since you already know her average for the first four, you can act as if she made that score on all four of them. So, your overall average would be (82+82+82+82+x)/5. That four tests of 82 each plus one you don't know, which is x.

82 x 4 = 328. So (328 + x)/5 = 84.

To get rid of the "divide by 5", multiply both sides by 5. Then you have 328 + x = 84 x 5, or 328 + x = 420.

Now you want to get the x completely by itself, so subtract 328 from both sides. x = 420 - 328, or x = 92. So Emily would need to make a 92 on her fifth quiz to make 84 overall.