SOLUTION: In a certain class there are 12 boys and 18 girls, if the average of class for an algebra exam is 90 and the boys average score is 87, what is the girls average score.

Question 861362: In a certain class there are 12 boys and 18 girls, if the average of class for an algebra exam is 90 and the boys average score is 87, what is the girls average score.

Answer by veerajgrewal(1) (Show Source): You can put this solution on YOUR website!
Given : Number of Boys= 12, Number of girls = 18
Average Marks of class = 90, Average marks of boys = 87
As we know that Average = (Sum of observations)/(Number of observations)
Now, (Total Marks)/(Total Students) = Avg marks of class
(Total Marks)/(12 + 18) = 90
Total Marks = 90*30 = 2700
Now, (Total Marks of boys)/(Number of Boys)= 87
(Total Marks of boys)/12= 87
Total Marks of Boys= 87*12
therefore, Marks of Boys = 1044
Now we know , Total Marks of class = Total Marks of Boys + Total Marks of Girls
Total marks of girls = Total Marks of class - Total Marks of Boys
Total marks of girls = 2700-1044 = 1656
Now Average of girls marks = (Total marks of girls)/(Number of girls)
= 1656/ 18
= 92
The answer is 92.

RELATED QUESTIONS
In a certain class, there are 14 boys and 21 girls. If the average score on an exam is 92 (answered by alicealc)

there are 30 boys and 60 girls in a class. if the average age of boys is 12 year and... (answered by TimothyLamb)

What is the detail solution of this question: In a class of 50 students the boys... (answered by stanbon)

In a class of 10 boys and 15 girls, the boys� average score on the final exam was 80 and... (answered by solver91311)

In a class there are 18 boys and 12 girls. What part of the class is... (answered by algebrahouse.com)

there are 18 boys and 12 girls what is the ratio of boys to students in the... (answered by jim_thompson5910)

a class has 12 boys and 18 girls. What is the percent of the students in the class are... (answered by MathMan88)

The average age of boys & girls in a class is 10.5 yrs. That of the boys is 10.6 & that... (answered by mananth,Fombitz)

If there are 15 boys in a class and 12 girls what percentage are the... (answered by ewatrrr)