Question

the average marks of students in a class is 69.2. The average marks of boys is 65 and that of girls is 72. what is the ratio of boys and girls?​

Answer 1

Answer:

2:3

Step-by-step explanation:

let boys =x ,girls = y

(65x + 72y)/x + y = 69.2

4.2x = 2.8y => 42x = 28y

x : y = 28 : 42 = 2 : 3

Answer 2

The ratio of boys and girls is 2 : 3

Solution:

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

$\frac{\text {total marks of boys}}{\text {number of boys}}=\text { Average marks of boys }$

$\Rightarrow \frac{\text {Total marks of boys}}{x}=65$

⇒ Total marks of boys = 65x

Now ,

$\begin{array}{l}{\frac{\text {total marks of girls}}{\text {number of girls}}=\text { Average marks of girls }} \\\\ {\Rightarrow \frac{\text { Total marks of girls }}{y}=72}\end{array}$

Total marks of girls = 72y

It is given that average marks of students in a class is 69.2  

$\Rightarrow \frac{\text {total marks of students}}{x+y}=69.2$

⇒ Total marks of students = 69.2 (x + y)

⇒ 65x + 72 y  = 69.2x + 69.2 y

⇒ 72y -69.2 y = 69.2x - 65x

⇒2.8y = 4.2x

⇒ x : y = 28:42

⇒ x :y = 2: 3

Thus the ratio of boys and girls is 2 : 3

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