Question

Cost of 9 pencil is equal to the cost of 4 pens.the cost of 13 pencils and six pence is 159.what is the cost of 21 pencil and 17 pencil together

Answer 1

let the cost of pencil be x,and the cost of pen be y.Then according to the question
9x=4y----------(i)
x=(4/9)y
it is also given that,
13x+6y=159
put the value of x
13(4/9)y+6y=159
(52/9)y+6y=159
by taking LCM as 9
(52y+54y)/9=159
(106y)/9=159
(106y)=159×9
y=(159×9)/106
y=13.5
Put the value of y in (i)
9x=4y
9x=4(13.5)
x=54/9
x=6
there fore we have to find
21x+17y=?
=21(6)+17(13.5)
=126+229.5
=355.5
hope it helps you
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Answer 2

Answer:

Total cost of 21 pencil and 17 pencil is 228

Step-by-step explanation:

Explanation:

Given , Cost of 9 pencil  is equal to the cost of 4 pens.

and Cost of 13 pencils and 6 pence = 159

Let the cost of each pencil be x and and cost of each pen be y

Step1:

∴Cost of 9 pencil = 9x and

Cost of 4 pens = 4y

⇒9x = 4y

⇒x = $\frac{4y}{9}$ .......(i)

Now ,Cost of 13 pencils = 13 x and

cost of 6 pens = 13 y

⇒ 13x + 6 y = 159 ..........(ii)

(given that cost of 13 pencil and pens is 159)

Step 2:

Put the value of x = $\frac{4y}{9}$ in equation (ii) we get ,

$13(\frac{4y}{9} ) + 6y = 159$

⇒ $\frac{52y}{9}+ 6y = 159$

⇒ $\frac{52y + 54y}{9} = 159$

⇒$\frac{106y}{9} = 159$⇒ $y= \frac{159 .(9)}{106}$

⇒ y = 13.5

Step 3:

Now put the value of y in any of the above equation ,

⇒$x = \frac{4y}{9}$ ⇒$\frac{4 (13.5)}{9}$ = 6

Therefore the cost of 21 pencil = 6 ×21 = 126 and

Cost of 17 pencil =17 ×6  = 102 .

Now, the total cost of 21 pencil and 17 pencil = 126 +102 = 228

Final answer :

Hence , the cost of 21 pencil and 17 pencil is 228.

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