Q18 of 102 Page 49

The total cost of the 5 books and 7 pens is ₹79 while the total cost of 7 books and 5 pens is ₹ 77. Find the total cost of 1 book and 2 pens.

Let cost of 1 book be x and cost of 1 pen be y


5x + 7y = 79 …equation (i)


7x + 5y = 77 …equation (ii)


Multiplying equation (i) by 7 and multiplying equation (ii) by 5 we get


35x + 49y = 553


35x + 25y = 385


Subtracting the above two equations we get


24y = 168


⇒ y = 7


5x + 49 = 79


⇒ 5x = 30


⇒ x = 6


Cost of 1 book and 2 pen = (6 + 14) = Rs. 20


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