Question

5 pencila and 7 pens together cost 50 rs

Answer 1

Answer:

Cost of 1 pencil = 3/-

Cost of 1 pen = 5/-

Step by step explanation:

Let the cost of 1 pencil & 1 pen be 'x' and 'y' resp.

Therefore we get 2 eqns.

$5x + 7y = 50$

$7x + 5y = 46$

By substitution method,

$5x + 7y = 50$

$5x = 50 - 7y$

$x = \frac{50 - 7y}{5}$

Put the value of x in 2nd eqn,

$7x + 5y = 46$

$7( \frac{50 - 7y}{5} ) + 5y = 46$

$\frac{350 - 49y}{5} + 5y = 46$

$\frac{350 - 49y + 25y}{5} = 46$

${350 - 24y} = 230$

$- 24y = 230 - 350$

$24y = 350 - 230$

$24y = 120$

$y = 5$

Put the value of y in eqn 1,

$5x + 7y = 50$

$5x + (7 \times 5) = 50$

$5x + 35 = 50$

$5x = 15$

$x = 3$

$x = 3 \: \\ y = 5$