5 pencils &7 pens together cost Rs.50 whereas 7 pencils & 5 pens together costs Rs. 46.find the cost of one pen & one pencil
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let the number of pencil be x
let the number of pen be y
5x + 7y = 50------(1)
7x + 5y = 46------(2)
(1) × 7 ==> 35x + 49y = 350
(2) × 5 ==> 35x + 25y = 230
(1) - (2) ==>
35x + 49y = 350
- 35x + 25y = 230
=0x + 24y = 120
y = 120 ÷ 24
= 5
(putting the value of y in (1) )
5x + 7×5 = 50
5x = 50 - 35
x=15÷5
x = 3
let the number of pen be y
5x + 7y = 50------(1)
7x + 5y = 46------(2)
(1) × 7 ==> 35x + 49y = 350
(2) × 5 ==> 35x + 25y = 230
(1) - (2) ==>
35x + 49y = 350
- 35x + 25y = 230
=0x + 24y = 120
y = 120 ÷ 24
= 5
(putting the value of y in (1) )
5x + 7×5 = 50
5x = 50 - 35
x=15÷5
x = 3
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