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If the profit per cent got on selling an article is numerically equal to its cost price in rupees and the selling price is Rs. 39, then cost price (in Rs.) will be:

A. 20

B. 22

C. 28

D. 30

Answer: Option D

Solution(By Examveda Team)

SP = Rs. 39
CP = x(let)
Profit % = CP
$${\text{or,}}\,\frac{{39 - x}}{x} \times 100 = x$$       $$\left[ {\% \,{\text{profit}} = \frac{{{\text{SP}} - {\text{CP}}}}{{{\text{CP}}}}} \right]$$
$$\eqalign{ & 3900 - 100x = {x^2} \cr & {x^2} + 100 - 3900 = 0 \cr } $$  
$$x=30$$   (we cannot take negative value of x)

This Question Belongs to Arithmetic Ability >> Profit And Loss

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Comments ( 7 )

  1. Ramesh Talwar
    Ramesh Talwar :
    1 year ago

    Just substitute the options:
    For eg:- if CP = 30 , SP = 39 (Given)
    Then gain = SP - CP i.e 39 - 30 = 9
    Then, Gain% = 9/30 * 100 = 30% which is same as CP.

  2. Sarayu Chintha
    Sarayu Chintha :
    5 years ago

    -130 and +30 are the roots.... Since we cannot take negative root... 30 is the answer

  3. Md Ibrahim
    Md Ibrahim :
    6 years ago

    39*100/130=30 (cp)
    39-30=9
    9/30*100=30%

  4. Poornima Sahu
    Poornima Sahu :
    6 years ago

    simple trick
    In this type of questions
    Sp ka is tarh fraction kro ki dono k bich 10 ka difference ho
    39 = 3*13
    Take 0 on both side
    30 and 130
    ans 130 nhi ho skta because that is more then sp
    so our answer is 30.

  5. Revathi Kannan
    Revathi Kannan :
    6 years ago

    3900-100x = x2
    x2+100x-3900 = 0 and not x2+100-3900 = 0
    Derivative, x2+100x-3900 has to be solved to arrive at an answer.

  6. Pabitra Gogoi
    Pabitra Gogoi :
    7 years ago

    please solve it x^2+100-3900=0

  7. Sudhakar Prajapati
    Sudhakar Prajapati :
    8 years ago

    Correct Answer = D

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