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?

Mean score of 90 students = 77.2

Step-by-step 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:

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

So, Sum of scores for School A = 3750

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

We know that:

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

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:

So, mean score of 90 students = 77.2

yes

step-by-step explanation:

they have to be opposite and reciprocal of eachother.