Question

On mixing two classes A and B of students having average marks 25 and 40 respectively, the overall average obtained is 30. Find the ratio of the students in the classes A and B.

Answer 1

Let the number of students in class A is x and class of B be yWe have to find x:y=x/y

Average marks of class A



$= \frac{Sum of A}{Number of students in A }$


[tex]25= \frac{Sum of A}{x} [/tex]




$25x = Sum of A$


Similarly,


$40y=Sum of B$
Adding both sums,

$25x+40y=Sum of A + Sum of B$





According to the question


[tex]Average of A and B= \frac{Sum of A + Sum of B}{x+y} [/tex]


$30(x+y)= Sum of A + Sum of B$



$Sum of A + Sum of B = 30x+30y$


THUS


$25x+40y=30x+30y$

[tex]-5x=-10y [/tex]


$\frac{x}{y} = \frac{2}{1}$
ANS:
x:y=2:1

Answer 2

Answer:2:1

Step-by-step explanation:

average marks of class A=25 (A1)

average marks of class B=40(A2)

overall average is obtained=30 (Aw)

ratio of the student in classes A and B = n1/n2 = (A2-Aw)/(Aw-A1)

n1/n2 = 10/5

n1:n2 = 2:1