Explanation:
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![\underline{ \underline{ \text{Given}}} :](https://img.qammunity.org/2022/formulas/mathematics/high-school/930b427lft1tjkl14cso23pyunmp15j7xd.png)
- CP of 11 pencils = SP of 10 pencils
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![\underline{ \underline{ \text{To \: find}}}:](https://img.qammunity.org/2022/formulas/mathematics/high-school/igy6hh47xfezsxlms652mg05yfbdkm6n79.png)
- Gain percent or loss percent
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![\underline{ \underline{ \text{Solution}}} :](https://img.qammunity.org/2022/formulas/mathematics/high-school/bezopcad47hrdqgoennkly63bs3drtumv5.png)
![\sf{CP\: of \: 1 \: pencil = x \: ( \: suppose})](https://img.qammunity.org/2022/formulas/mathematics/high-school/fee8fxnrp28iozsff8f5548mijxdwraukx.png)
![\sf{CP \: of \: 11 \: pencils = 11x}](https://img.qammunity.org/2022/formulas/mathematics/high-school/vvtjv89fezd078g0b6k03uesdgnrngell3.png)
{ Since CP of 15 articles is equal to SP of 12 )
![\sf{SP \: of \: 1 \: pencil = (11)/(10) x}](https://img.qammunity.org/2022/formulas/mathematics/high-school/rimizn24ozkscd4ielep4yqh423q2uvzzm.png)
Here , SP > CP. So, He / she made a profit.
![\boxed{ \sf{Profit = SP - CP}}](https://img.qammunity.org/2022/formulas/mathematics/high-school/i0jiy9chp94ahw9ja16wi32678hjwdwzyk.png)
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![\sf{ (11)/(10) x - x}](https://img.qammunity.org/2022/formulas/mathematics/high-school/if77ow5yb1ltawxannny63gsgzow4ty2pq.png)
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![\sf{ (11x - 10x)/(10)}](https://img.qammunity.org/2022/formulas/mathematics/high-school/14jtj9a67j1f0dmzqgupbraz3rgzs0x5vy.png)
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![\sf{ (x)/(10) }](https://img.qammunity.org/2022/formulas/mathematics/high-school/lzhvt7jo9mc6azbnj5sws79g9zvu8nyic9.png)
Now , Finding the profit percentage :
![\boxed{ \sf{Profit\% \: = (Profit)/(CP) * 100\%}}](https://img.qammunity.org/2022/formulas/mathematics/high-school/56bgc55iigt7vfciqkf5uozzvehth85ldw.png)
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![\sf{ ( (x)/(10) )/(x) } * 100\%](https://img.qammunity.org/2022/formulas/mathematics/high-school/q9px5v88jiue06lj8a2fltmlwfoc37thon.png)
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![\sf{ (x)/(10) * (1)/(x) * 100\%}](https://img.qammunity.org/2022/formulas/mathematics/high-school/ai228auaoz5jk8p1f20v93msmw6bpp8r5i.png)
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![\sf{ \frac{ \cancel{x}}{10} * \frac{1}{ \cancel{x} } * 100\%}](https://img.qammunity.org/2022/formulas/mathematics/high-school/y2dm77o0jake5izyi9wivjfo7d4z4gpufh.png)
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![\sf{ (1)/(10) * 100\%}](https://img.qammunity.org/2022/formulas/mathematics/high-school/t55a79157h8w920m5m2o50tyo6ll1q6pvs.png)
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![\boxed{ \sf{10\%}}](https://img.qammunity.org/2022/formulas/mathematics/high-school/94giuwpd094cnfk4hmpxjstnlvfk0m3jag.png)
![\purple{ \boxed{ \boxed{ \tt{⇢Our \: final \: answer : 10\% \: \: profit}}}}](https://img.qammunity.org/2022/formulas/mathematics/high-school/pl7p6g8dy70m3nq94smnncivv38r4d1m5p.png)
Hope I helped ! ♡
Have a wonderful day / night ツ
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