Form the pair of linear equations in the following problems, and find their solutions graphi cally

Solution:

(i) Let the number of boys be x and the number of girls be y.
According to the given conditions

$x+y=10$ and $y=x+4$

We get the required pair of linear equations as

$x+y-10=0, x-y+4=0$



Graphical Solution

$x+y-10=0$...(1)



$x-y+4=0 \quad \ldots$...(ii)



From the graph, we have : x = 3, y = 7 common solution of the two linear equations.

Hence, the number of boys = 3 and the number of girls = 7.

(ii) Let the cost of 1 pencil be Rs $x$ and cost of 1 pen be Rs. $y$.

$5 x+7 y=50$

$7 x+5 y=46$

$7 x+5 y=46$

5x + 7 y = 50° 7x + 5x = 46





From the graph we have x = 3, y = 5.

Hence, cost of one pencil = Rs.3 and cost of

one pen = Rs.5