Question

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In a mathematics test the average marks of boys is x % and average marks of girls is y % with
x not equal to y. If average marks of all student are z% the ratio of number of girls to total number of
student is?​

Answer 1

Answer:

it could be x:y=z hopefully it is not wrong

Answer 2

Given : average marks of boys is x % and average marks of girls is y %

To find : ratio of number of girls to total number of  student

Explanation:

Let the total number of the boys be a

and total number of girls be b

then according to question

(a+b) z = ax+by

then

$z= \left ( \frac{a}{a+b} \right )x+\left ( \frac{b}{a+b} \right )y$

now , let te ratio of the number of girls to the number of students be c

then ratio of the number of the boys to the total number of the students will be 1-c

therefore ,

z = (1-c)x+cy

$c = \frac{z-x}{y-x}$

where c is he ratio of number of girls to total number of  student

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