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March 25, 2017

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Arjun spent Rs.12 to purchase some pens and pencils.The cost of a pen and pencil are in the ratio 3:2.
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 - ,

    let 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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