Chapter I : Linear Equations in two variables in two variables

Example 20. Students of a class are made to stand in rows. If 4 students are extra in a row, there if would be 2 rows less. if 4 students are less in a row, there would be 4 more roes. Find the number of student in the class.

Solution:- Let number of students be x, number of students in a row be y and number of rows be n

A/Q x = (n - 2) (y + 4)

ny = ny + 4n - 2y - 8

Or,   4n - 2y - 8 = 0 ----------------- (2)

Or,   2n - y - u = 0

and x = (n + 4) (y - 4)

ny = ny - 4n + 4y - 16

Or,   -4n + 4y - 16 = 0

Or,   -n + y - u = o -------------------- (3)

Adding (2) & and (3)

From (3) y = n + 4 = 8 + 4 = 12