Question

plz solve this Word problem class 10th only by substitution method. ​

Answer 1

$\bold\red {ANSWER}$

Let the number of rows be x and number of students in a row be y.

Total students of the class= Number of rows × Number of students in a row

=x×y=xy

Case 1

Total number of students =(x−1)(y+3)

⇒xy=(x−1)(y+3)=xy−y+3x−3

⇒3x−y−3=0

⇒3x−y=3-----(i)

Case 2

Total number of students=(x+2)(y−3)

⇒xy=xy+2y−3x−6

⇒3x−2y=−6--------(ii)

Subtracting equation (ii) from (i),

⇒(3x−y)−(3x−2y)=3−(−6)

⇒−y+2y=3+6

⇒y=9

By substituting value of y in (i), we get

⇒3x−9=3

⇒3x=9+3=12

⇒x=4

Number of rows =x=4

Number of students in a row =y=9

Number of total students in a class =x×y=4×9=36