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March 30, 2015

March 30, 2015

Posted by **Anonymous** on Wednesday, January 16, 2013 at 11:34am.

the total cost of a pen and a pencil is Rs. 3.

if the total number of pens and pencils he purchased is7,

find the number of pens he purchased.

- maths-urgent -
**Reiny**, Wednesday, January 16, 2013 at 4:22pmlet the cost of a pen be 3x

let the cost of a pencil be 2x , ( notice 3x : 2x = 3:2 )

number of pens --- a

number of pencils --- 7-a , because their sum is 7

3x + 2x = 3

5x = 3

x = Rs 3/5 = Rs 0.6

so a pen costs Rs 1.8

and a penci costs Rs 1.2

1.8a + 1.2(7-a) = 12

1.8a + 8.4 - 1.2a = 12

.6a = 3.6

a = 6

so there were 6 pens purchased and 1 pencil

check:

1+6 = 7 , number of pens and pencils checks!

cost of pen = 1.8

cost of pencil = 1.2

ratio is 1.8 : 1.2 = 3 : 2 , ratio costs checks!

6pens + 1 pencil = 6(1.8) + 1.2 = 12

All looks good!

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