Question

C 17. At high school A, the mean score of 50 students on a science test is 75.

At high school B, the mean score of 40 students on the same test is 80.
What is the mean score of the 90 students?

Answer 1

Mean score of 90 students = 77.2

Explanation:

Mean score of 50 students from school A = 75

Mean score of 40 students from school B = 80

We need to find mean score of the 90 students?

First we will find sum of scores of students from school A

We know that:
`Average=(Sum\:of\:Terms)/(Number\:of\:terms)`

We have Average = 75, Number of terms = 50, We need to find Sum of terms (scores)

`Average=(Sum\:of\:Terms)/(Number\:of\:terms)\\75=(Sum\:of\:Terms)/(50)\\Sum\:of\:Terms= 75* 50\\Sum\:of\:Terms=3750`

So, Sum of scores for School A = 3750

Now, we will find sum of scores of students from school B

We know that:
`Average=(Sum\:of\:Terms)/(Number\:of\:terms)`

We have Average = 80, Number of terms = 40, We need to find Sum of terms (scores)

`Average=(Sum\:of\:Terms)/(Number\:of\:terms)\\80=(Sum\:of\:Terms)/(40)\\Sum\:of\:Terms= 80* 40\\Sum\:of\:Terms=3200`

So, Sum of scores for School B = 3200

Now, We will find mean score of the 90 students?

Mean score of 90 students will be:

`Average=(Sum\:of\:Terms)/(Number\:of\:terms)\\Average=(3750+3200)/(90)\\Average=(6950)/(90)\\Average = 77.2`

So, mean score of 90 students = 77.2