8th Class Mathematics Percentage Question Bank Percentage, Profit and Loss

  • question_answer By selling 100 pens, a shopkeeper gains the selling price of 20 pens. Find his gain percent?

    A)  10%                            

    B)  15%         

    C)  30%                            

    D)  25%

    Correct Answer: D

    Solution :

    (d): Let C.P of one pen = x Let gain % be p% \[\Rightarrow S.P.\left( one\text{ }pen \right)=x\times \left( \frac{100+p}{100} \right)\] On sale of 100 pens, S.P of 100 pens \[=100x\left( \frac{100+p}{100} \right)\] For 100 pens, gain \[=S.P-C.P=x\left( 100+p \right)-100x\] This gain = S.P (20 pens) \[=20x\times \left( \frac{100+p}{100} \right)\] \[\Rightarrow px=\frac{x\left( 100+p \right)}{5}\] \[\Rightarrow 5px=100x+px\] \[\Rightarrow 4px=100x\] \[\Rightarrow 4p=100=p=20\,or\,25%\]

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