Question

Five books and 7 pens together cost Rs 79 7 books and 5 pens together cost
rupees 77 find the cost of two books and one pen

Answer 1

Heya!
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✴Let the cost of one book be Rs.x

✴Let the cost of one pen be Rs.y

♦According to the given question =>
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==> 5x + 7y = 79...................(1 )

==> 7x + 5y = 77..................(2 )

✳Solving (1) and (2) by Elimination Method :-
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♦Step1.
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♦Multiply Eq. (1 ) by 7 and Eq.(2) by 5 to make the coefficients same .

=> 7 ( 5x + 7y = 79 )

=> 35x + 49y = 563...............(3)

.

=> 5 ( 7x + 5y = 77 )

=> 35x + 25y = 385.................(4)

♦Subtracting (4) from (3)

=> ( 35x - 35x ) + ( 49y - 25y ) = ( 563 - 385 )

=> 24y = 168

=> y = 7
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♦Put y = 7 in Eq. (1)
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=> 5x + 7(7) = 79

=> 5x + 49 = 79

=> 5x = 30

=> x = 6
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✴NOW ,
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♦Cost of 2 Books and 1 pen =>

=>> 2x + y

=> 2(6) + 7

=> 12 + 7

=> Rs.19

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