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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:
Answer & Solution
Correct Answer:
Option
D
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)
$$\eqalign{ & 3900 - 100x = {x^2} \cr & {x^2} + 100 - 3900 = 0 \cr } $$
$$x=30$$ (we cannot take negative value of x)
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LoginFor 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.
39-30=9
9/30*100=30%
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.
x2+100x-3900 = 0 and not x2+100-3900 = 0
Derivative, x2+100x-3900 has to be solved to arrive at an answer.