Question

the ratio of girls and boys in class is 1:3 set an equation between the student of a class and boys and then draw it's graph also find the number of boys in a class of boys in a class of 40 students from the graph

Answer 1

Let no. of girls be x and boys be 3x
Total no. of students= 40
x+3x=40
x=10
Therefore the no of boys= 3x= 30
Now, the equation
Let the no. of boys be x and girls be y
Therefore,
The equation= x+y=40

Answer 2

In class the boys in total are 10.

Solution:

Given: Total number of boys and girl = 40, Ratio = 1 : 3

Number of girls be A and Number of boys be B.

Ratio of number of girls and boys is 1 : 3, so $\frac{A}{B}=\frac{1}{3}$

Therefore 3A=B

To find number of boys we use the ratio 1+3=4  

Therefore the number of boys, $\frac{B}{(A+B)} \times 40=\frac{3}{4} \times 40=10$

Number of girls = Total number of girls and boys – Number of boys = 40 – 10 = 30 girls

Now we can also find number of boys using graphical method.

To write the equation in graphical form we know that A = 10 and B = 30 so it can be written as A = A and B = 3A

The total number of boys and girls = 4A, So plot the graph of A, 3A, 4A and A = 10 which is showed attached image below.

As we can see that (10, 10) represents the number of boys in the graph, whereas in point (10, 30) the number 30 represents the number of girls. 40 as total on the line A = 10, which is the common equation.