Question

5 pencils and 7 pens together cost rupees 195 while 7 pencil and 5 pens together cost Rs 153.
find the cost of each one of the pencil and the pen.

Answer 1

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→ Let the cost of one pencil be ₹x.

→ And, the cost of one pen be ₹y.


▶ Now,

A/Q,

=> 5x + 7y = 195.............(1).


And, again

=> 7x + 5y = 153...............(2).

➡ Solving by Elimination method:-)

→ Multiply equation (1) by 7, and equation (2) by 5.

=> 7( 5x + 7y = 195 )

=> 35x + 49y = 1365..............(3).

And,

=> 5( 7x + 5y = 153 )

=> 35x + 25y = 765............(4).


▶Now, Substracte equation (3) and (4), we get

35x + 49y = 1365
35x + 25y = 765
(-)......(-)........(-)
______________

=> 24y = 600.

=> y = 600/24.

=> y = 25.

➡ Putting the value of ‘y’ in equation (1).

=> 5x + 7 × 25 = 195.

=> 5x + 175 = 195.

=> 5x = 195 - 175.

=> 5x = 20.

=> x = 20/5.

=> x = 4.

✔✔ Hence, the cost of one pencil is ₹4.
And, the cost of one pen is ₹25. ✅✅

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Answer 2

→ Let the cost of one pencil be ₹x.

→ And, the cost of one pen be ₹y

=> 5x + 7y = 195.............(1).


And, again

=> 7x + 5y = 153...............(2).




=> 7( 5x + 7y = 195 )

=> 35x + 49y = 1365..............(3).


5( 7x + 5y = 153 )

=> 35x + 25y = 765............(4).

Now, Substracte equation (3) and (4), we get



=> 24y = 600.

=> y = 600/24.

=> y = 25.

Putting the value of ‘y’ in equation (1).

=> 5x + 7 × 25 = 195.

=> 5x + 175 = 195.

=> 5x = 195 - 175.

=> 5x = 20.

=> x = 20/5.

=> x = 4.