Question

m 5 pencils and 7 pens together cost 50, whereas 7 pencils and 5 pens together
cost ? 46. Find the cost of one pencil and that of one pen.
​

Answer 1

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

Now, Cost of 5 pencils = Rs. 5x

Cost of 7 pens = Rs. 7y

5x + 7y = 50 --> ( i )

Similarly,

7x + 5y = 46 ---> ( ii )

From equation ( i ),

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

Putting value of ' x ' in equation ( ii ),

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

350 - 49y + 25y = 230

-24y = 230 - 350

-24y = - 120

y = $\frac{120}{24}$

$\fbox{\tt{y \:= \:5}}$

Putting value of 'y' in 'x',

x = $\frac{50\: - \:7*5} {5}$

x = $\frac{50\: - \:35} {5}$

x = $\frac{15} {5}$

$\fbox{\tt{x \:= \:3}}$

➡️ Cost of one pencil = Rs. 3

➡️ Cost of one pen = Rs. 5