Question

5 pencils and 7 pens together cost Rs.50, where as 7 pencils and 5 pens together cost Rs.46. Find

the cost of one pencil and that of one pen.​

Answer 1

Step-by-step explanation:

Let the cost of one pencil be 'x' and the cost of one pen be 'y'.

From the question,

$5x + 7y = 50$

Also,

$7x + 5y = 46$

By solving, we get

$5x + 7y + 7x + 5y = 50 + 46 \\ 12x + 12y = 96 \\ x + y = 8 \\ x = 8 - y$

Now,

$5x + 7y = 50 \\ 5(8 - y) + 7y = 50 \\ 40 - 5y + 7y = 50 \\ 2y = 10 \\ y = 5$

So,

$x = 8 - y \\ x = 8 - 5 \\ x = 3$

Hence, cost of one pencil is RS 3

Cost of one pen is RS 5.

Thank you