there are 15 boys and 13 girls in a class. In a maths test the mean mark for the boys was B. In the same test the mean mark for the girls was G. Write down an expression for the mean mark of all 28 pupils.
2006-11-08 07:36:55 · 16 answers · asked by xx gemma xx 1 in Science & Mathematics ➔ Mathematics
(15B + 13G)/28
2006-11-08 07:38:44 · answer #1 · answered by Nobody 3 · 1⤊ 0⤋
(15B+13G)/28=n
where n is equal to the mean.
Explanation:
To get a mean, you must divide the sum of the scores by the amount of scores. Thus, if there are 15 boys who had an average of B, then you must figure that the sum was equal to 15B (because 15B divided by 15 is B). Same with the girls.
Adding these two sums together gives you the sum of the grades of the entire class. Dividing by 28 gives you the mean grade of the class.
Hope I helped.
Here's a page on how to do these types of problems:
http://www.hawaii.edu/suremath/k4_12dir/meanScore.html
2006-11-08 07:43:21 · answer #2 · answered by fire_leo_805 3 · 0⤊ 0⤋
(15B + 13G) / 28 = mean of all 28 students
B is the total of each boy's individual score divided by 15...so if you multiply it by 15, you will have the total number of the boy's score. DO the same with the girls (using 13 since that is the number of girls). When you add the two numbers together that is the same as if you added each of the 28 individual numbers together. Divide by 28 to get the whole class' mean score.
2006-11-08 07:40:35 · answer #3 · answered by chubbiecheeks 2 · 0⤊ 0⤋
B+G=28
15+13=28
B+G=P
2006-11-08 07:45:16 · answer #4 · answered by orangemonkey_04 2 · 0⤊ 0⤋
(15/28)*B+(13/28)*G
2006-11-08 07:40:56 · answer #5 · answered by bruinfan 7 · 0⤊ 0⤋
2 points thx genius
2006-11-08 07:49:24 · answer #6 · answered by Mr Rogers best friend 2 · 0⤊ 0⤋
Boys are > girls who are nothing < dense.
2006-11-09 10:16:20 · answer #7 · answered by alan d 1 · 0⤊ 0⤋
I'm not THAT bored. But I see some people are.
2006-11-08 07:40:57 · answer #8 · answered by Simon K 3 · 0⤊ 1⤋
Yawn! No I don't think I'm bored enough yet..
2006-11-08 11:14:11 · answer #9 · answered by bo nidle 4 · 0⤊ 0⤋
I am bored, but too drunk to answer your question.
2006-11-08 07:52:31 · answer #10 · answered by Kirsty 7 · 0⤊ 0⤋