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The Total Cost of 6 Books and 7 Pens is 79 Rupees and the Total Cost of 7 Books and 5 Pens is 77 Rupeess. Find the Cost of 1 Book and 2 Pens. - Algebra

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Sum

The total cost of 6 books and 7 pens is 79 rupees and the total cost of 7 books and 5 pens is 77 rupeess. Find the cost of 1 book and 2 pens.

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Solution

Disclaimer: There is an error in the given question. Instead of 7 books and 5 pens there should be 7 books and 6 pens. 

Let the cost of 1 book be x and the cost of 1 pen be y. 
The total cost of 6 books and 7 pens is 79 rupees.
6x + 7y = 79                                          .......(I)
Total cost of 7 books and 6 pens is 77 rupeess.
7x + 6y = 77                                        .........(II)
Adding (I) and (II)
13x + 13y = 156
⇒ x + y = 12                                        ..........(III)
Subtracting (II) from (I)
- x + y = 2                                            ..........(IV)
Adding (III) and (IV)
2y =14
⇒ y = 7
⇒ x = 5
So, the cost of one book is 5
And one pen is 7
So, Cost of 1 book and 2 pens is
x + 2y = 5 + 2(7) = 5 + 14 = Rs. 19

Concept: Algebraic Methods of Solving a Pair of Linear Equations - Elimination Method
  Is there an error in this question or solution?
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APPEARS IN

Balbharati Mathematics 1 Algebra 9th Standard Maharashtra State Board
Chapter 5 Linear Equations in Two Variables
Problem Set 5 | Q 6 | Page 92
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