Question

Abby scored 88, 91, 95, and 89 on her first four history quizzes. What score does Abby need to get on her fifth quiz to have an average of exactly 90 on her history quizzes? a.85b.86c.87a.88

Answer 1

For this case we can use the definition of average given by:

`\text{Mean}=(x_1+x_2+x_3+x_4+x_5)/(5)`

The final score needs to be 90 so we can do this:

`90=(88+91+95+89+x_5)/(5)`

And solving for x5 we got:

5*90 = 88+91+95+89+ x5

x5= 450 - 88- 91- 95 -89 = 87

Final answer:

c.87