Question

5 pencils and 7 pens together cost Rupees 50 where as 7 pencils and 5 pens together cost rupees 46 find the cost of 1 pencils and that of 1 pen

Answer 1

 5 pencils and 7 pens together cost Rs 50, whereas 7 pencils and 5 pens together cost Rs 46. Find the cost of one pencil and that of one pen

Let cost of pencil      = Rs x

Cost of pens             = Rs y

5 pencils and 7 pens together cost Rs 50,

So we get

5x + 7y = 50

Subtract 7y both side we get

5x        = 50 – 7 y

Divide by 5 we get

X         = 10  - 7 y /5

Plug value of y which is factor of 5 to get whole number so plug y = 5 , 10  and 15 we get

x         = 10 – 7 * 5 / 5    = 10 – 7  = 3

x         = 10 – 7 * 10 / 5  = 10 – 14 = - 4

x         = 10 – 7 * 15 / 5  = 10 – 21  = - 11

X

3

-4

-11

y

5

10

15

Given that 7 pencils and 5 pens together cost Rs 46

7  x + 5 y       = 46

Subtract 7x both side we get

5y        = 46 – 7x

Divide by 5 we get

y         = 46 / 5   - 7 x / 5

y         = 9.2 – 1.4  x

Plug x  = 0 , 2 and 4 we get

y         =  9.2 – 1.4 * 0   = 9.2 – 0   = 9.2

                                   y     =  9.2 – 1.4 (2)   = 9.2 – 2.8  = 6.4

y        =  9.2 – 1.4 (4)    = 9.2 – 5.6  = 3.6

X

0

2

4

Y

9.2

6.4

Answer 2

let cost of pencil = x
pen = y
so, 5x + 7y = 50 ----------------(1)
7x + 5y = 46 ------(2)
adding 1 &2
X + y = 8 --------(3)
multiply '5' for (3)
5x + 5y =40 ------(4)
subtract 4 from 2
2x= 6
X=3
so , no of pencils are 3
no of pens are 5 (from 3)


Dear friend I hope it's helpful to you so please mark my answer as brainlist.......