Question

the quiz
(ii) 5 pencils and 7 pens together cost * 50, whereas 7 pencils and 5 pens together
cost 46. Find the cost of one pencil and that of one pen.
the​

Answer 1

Explanation:

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

3.6

Answer  cost of 1 pencil = Rs 3 Cost of 1 pen = Rs 5