Question

The cost of 5 books and 7 pens together is Rs 79 where as the cost of 7 books and 5 pens together is Rs 77 . Find the cost of 1 book and 2 pencils.

Answer 1

ATQ

5x+7y = ₹79

7x+5y = ₹77

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12x+12y = ₹156

12(x+y) = ₹156

x+y = ₹156/12

x+y = ₹13

x = ₹13-y

Putting the above value of x in any of the above two equations.

5(13-y)+7y = ₹79

65-5y+7y = ₹79

2y = ₹14

y = ₹7

x = ₹13-₹7 = ₹6

Cost of 1 book = ₹6

Cost of 2 pens = 2y = ₹2*7 = ₹14