Question

Elena must have an average of at least 90 in Math to compete in the Math Olympiad.

Her current math test scores are 81, 85, 91, 97, and 90 on the first five tests.
What is the minimum score she must attain on the sixth test to achieve an average of 90
("rounding up to 90" is not allowed)

Answer 1

Answer: The minimum score she must attain is a 96.

Explanation:

We will set up an equation to help us solve for the sixth test score. The average can be found by adding all the numbers together and dividing by the numbers of number.

`\displaystyle (81+85+91+97+90+x)/(6) =90`

Next, we will solve.

Given:

`\displaystyle (81+85+91+97+90+x)/(6) =90`

Multiply both sides by 6:

`\displaystyle 81+85+91+97+90+x =540`

Add like terms together:

`\displaystyle 444+x =540`

Subtract 444 from both sides of the equation:

`x=96`