Question 6 of 19

Leon knows that his first four test grades were 78, 86, 82, and 88.

Use the formula:

[tex]\[ \text{Average} = \frac{x_1 + x_2 + \ldots + x_n}{n} \][/tex]

to find Leon's grade on the fifth test if his test average is 83.8.



Answer :

To determine Leon's grade on the fifth test given that his average test grade is 83.8, we can follow these steps:

1. Determine the number of tests:
Leon has taken five tests in total.

2. Calculate the total grade sum required to achieve the average:
Since the average grade is 83.8 and there are 5 tests, the total sum of all test grades should be:
[tex]\[ \text{Total Sum} = \text{Average Grade} \times \text{Number of Tests} \][/tex]
[tex]\[ \text{Total Sum} = 83.8 \times 5 = 419.0 \][/tex]

3. Sum the grades of the first four tests:
We know the first four grades are:
[tex]\[ \text{Grade 1} = 78 \][/tex]
[tex]\[ \text{Grade 2} = 86 \][/tex]
[tex]\[ \text{Grade 3} = 82 \][/tex]
[tex]\[ \text{Grade 4} = 88 \][/tex]
Then, sum the first four grades:
[tex]\[ \text{Sum of first four grades} = 78 + 86 + 82 + 88 = 334 \][/tex]

4. Calculate the fifth grade:
To find the grade for the fifth test, subtract the sum of the first four grades from the total sum of all grades needed to achieve the average:
[tex]\[ \text{Grade 5} = \text{Total Sum} - \text{Sum of first four grades} \][/tex]
[tex]\[ \text{Grade 5} = 419.0 - 334 = 85.0 \][/tex]

So, Leon needs to score 85 on his fifth test to achieve an average score of 83.8 across all five tests.