Question
Form the pair of linear equations in the following problems, and find their solution graphically:
10 students of class X took part in Mathematics quiz. If the number of girls is 4 more than the number of boys, find the number of boys and girls who took part in the quiz.

Answer

Let the number of girls and boys in the class be x and y respectively.
According to the given conditions, we have,
x + y = 10
x - y = 4
x + y = 10
⇒ x = 10 - y
Three solutions of this equations can be written in a table as follows,
x
4
5
6
y
6
5
4
x - y = 4
⇒ x = 4 + y
Three solutions of this equation can be written in a table as follows.
x
5
4
3
y
1
0
-1
The graphical representation is as follows.

From the graph, it can be observes that the two lines intersect each other at the point (7, 3). So. x = 7 and y = 3. Thus the number of girls and boys in the class are 7 and 3 respectively.

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