Question

The average of marks obtained by the students in a class is 72.the average mark of the girls in the class is88 and that of boys is 68.what is the percent of girls to boys in the class room

Answer 1

total students=x
total girls=y
total marks 72x,marks of girls=88y,

marks of boys=72x-88y=68(x-y)
4x=20y
x/y=5/1,x-y=boys=5-1=4
boys=4
girls=1
%age= (1/4)×100=25%

Answer 2

Answer:

25%

Step-by-step explanation:

Let x be the number of girls and y be the number of boys

So, total students = x+y

The average of marks obtained by the students in a class is 72.

$72 =\frac{\text{Sum of all marks}}{\text{Total students}}$

$72 =\frac{\text{Sum of all marks}}{x+y}$

$72(x+y) =\text{Sum of all marks}$

The average mark of the girls in the class is 88

$72 =\frac{\text{Sum of marks of girls }}{x}$

$72x =\text{Sum of marks of girls }$

The average mark of the boys in the class is 68

$68 =\frac{\text{Sum of marks of boys }}{y}$

$68y =\text{Sum of marks of girls }$

Total marks of class= total marks of all boys + total marks of all girls

$72(x+y)=68y+88x$

$72x+72y=68y+88x$

$16x=4y$

$4x=y$

$\frac{x}{y}=\frac{1}{4}$

ratio of girls to boys = 1:4

Let teh ratio be a

So, No. of girls = a

No. of boys = 4a

The percent of girls to boys in the class room=$\frac{a}{4a} \times 100$

                                                                           =$25\%$

Hence  the percent of girls to boys in the class room is 25%