Question

Example 9: Let us consider Example 2 in Section 3.3, i.e., the cost of 2 pencils and
3 erasers is Rs 9 and the cost of 4 pencils and 6 erasers is Rs 18. Find the cost of each
pencil and each eraser.​

Answer 1

Step-by-step explanation:

$let \: the \: cost \: of \: pencil \: be \: x \ \: and \: let \: the \: cost \: of \: eraser \: be \: y$

Romila purchased two pencils and three erasers for rupees 9

i.e. 2×(cost of pencil)+3×(cost of eraser )=9

2x+3y=9

also Sonali purchased 4pencils and 6 erasers for RS 18

i.e. 4×(cost of pencil)+6×( cost of eraser)=18

4x+6y=18

solve our two equations are

1)2xy +3y=9

2)4x +6y =18

putting value of x in (2)

4x+6y=18

4(9-3y) +6y =18

2

2(9-3)+6y=18

18-6y +6y=18

18=18

it is true for all values x and y .

note= we can not open the specific value of x and y because both the equation given are same .