averages topic

Question

in a class of 21 students the average score on math test was 77% if suzie got 95% and jack got 78% what is the average grade of the other 19 students?

 

(a)89%

(b)85%

(c)80%

(d)75%

Answer 1

first i would calculate the total score for the entire class

21 students x 77% = 1617

meaning that if Suzie and Jack had 95 + 78 = 173, then the remaining students had

1617 - 173 = 1444

to find the average then you can just divide by 19 since there are 19 other students

1444 / 19 = 76%

meaning that the average grade of the other 19 students is 76%

Answer 2

We know that to find the average of a group of numbers you sum up the numbers and

divide the total by the # of number in the set...

 

Given a total of 21 students, 2 of which got a 95 and a 78 we can find the total of the

other 19 students grades:

 

(95 + 78 + x)/21 = 77    where x is the total sum of the other 19 grades

 

173+x=77(21)

x = 77(21)-173

x = 1444

 

The 19 other grades totaled to 1444

To get the average divide the sum by the number of entries....

 

1444/19 = 76

 

I have done this twice with the same answer.... 76%  so I would go with answer d