Question

Javier earned the following scores on his first five tests: 77, 89, 84, 80, and 85. What score did he earn on his last test to have a test mean of 84%?

Answer 1

Given:

Javier earned the following scores on his first five tests: 77, 89, 84, 80, and 85.

To find:

What score did he earn on his last test to have a test mean of 84?

Solution:

The no. of tests = 5

The sum of the first five tests = 77 + 89 + 84 + 80 + 85 = 415

The mean of six tests = 84

Let's assume "x" represents the last test score earned by Javier.

We know,

$\boxed{\bold{Average\:or\:Mean = \frac{Sum\:of\:observations}{No. \:of\:observations} }}$

Therefore, based on the formula above we can form the equation for the mean of 6 tests as:

$\frac{415 + x}{6 } = 84$

$\implies 415 + x = 84 \times 6$

$\implies 415 + x = 504$

$\implies x = 504 - 415$

$\implies \bold{x = 89}$

Thus, Javier earned a score of 89 on his last test to have a test mean of 84.

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