Question

1. If the cost of 2 pencil and 3 pen is 120 and the cost
of 5 pencil and 2 pen is * 190. What is the cost of
8 pencil and 9 pen.​

Answer 1

Question:-

If the cost of 2 pencil and 3 pen is 120 and the cost of 5 pencil and 2 pen is 190. What is the cost of 8 pencil and 9 pen.

Solution:-

{ According to question }

• The cost of 2 pencil and 3 pen is 120
• The cost of 5 pencil and 2 pen is 190

Let, x be the cost of one pencil & y be the cost of one pen.

Now, according to question & assumption

we from an equation

—› 2x + 3y = 120 ........ ( 1 )

—› 5x + 2y = 190 ........ ( 2 )

{To find value of x ( pencil ) }

multiply eq. ( 1 ) by 5, we get,

—› 10x + 15y = 600 ....... ( 3 )

multiply eq. ( 2 ) by 2, we get

—› 10x + 4y = 380 ....... ( 4 )

Now, subtract eq. ( 4 ) from eq. ( 3 )

10x + 15y = 600

- ( 10x + 4y = 380 )

____________________

11y = 220

y = 220/11

y = 20

{To find value of y ( pen ) }

Now, put value of y in eq. ( 1 )

—› 2x + 3y = 120

—› 2x + 3( 20 ) = 120

—› 2x + 60 = 120

—› 2x = 120 - 60

—› 2x = 60

—› x = 60/2

—› x = 30

from value of x & y we know cost of one pencil is {unit} 20 & cost of one pen is {unit} 30 respectively.

Now, for cost of 8 pencil's and 9 pen's.

—› Cost of 8 pencil's =

[cost of one pencil's]×[quantity of pencil's]

—› Cost of 8 pencil's = 20 × 8

—› Cost of 8 pencil = {unit} 160

—› Cost of 9 pen's

= [cost of one pen's]×[quantity of pen's]

—› Cost of 9 pen's = 30 × 9

—› Cost of 9 pen's = {unit} 270

Hence cost of 8 pencil's is {unit} 160 & cost of 9 pen's is {unit} 270 .

Hope it helps you.