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Bunuel
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P+Q+(P*Q)/100=0
the only answer that's fits in this equation for subsequent percentage changes is the correct solution
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I like the solution - it’s helpful.
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Hi Bunuel,

Thank you for the clear explaination.

I just want to make sure

To get 100+25, donwe need to break down each prime number of the possible p below before finally decide with the 125? Or any other way to get 125 directly?



[ltr]100+p[/ltr]
, we get: 110, 115, 120, 125, 150, and 175. Only 125 does not have primes other than 2 and 5.


Bunuel
Official Solution:


The number of employees after \(p\%\) increase and \(q\%\) decrease would be \(x(1 + \frac{p}{100})(1 - \frac{q}{100})\). Since at the end the company had the same number of employees, we get:

\(x(1 + \frac{p}{100})(1 - \frac{q}{100})=x\)

\((1 + \frac{p}{100})(1 - \frac{q}{100})=1\)

\((\frac{100+p}{100})(\frac{100-q}{100})=1\)

\((100+p)(100-q)=100*100\)

Now, we need to find the values of \(p\) and \(q\) that satisfy this equation. Notice that the right-hand side, \(100 * 100 = 10^4\), has only 2 and 5 as its prime factors. Thus, the left-hand side must also have only these primes. Substituting different values of \(p\) from the options for \(100 + p\), we get: 110, 115, 120, 125, 150, and 175. Only 125 does not have primes other than 2 and 5. Hence, \(p\) must be 25. Increasing something by \(25\%\) needs to be decreased by \(20\%\) to bring it back to the original value, making \(q\) equal to 20.


Correct answer:

p "25"

q "20"
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Hi Bunuel,

Thank you for the clear explaination.

I just want to make sure

To get 100+25, donwe need to break down each prime number of the possible p below before finally decide with the 125? Or any other way to get 125 directly?




No. You do not need full prime factorization. Just note that (100 + p) must be a factor of 10000 and greater than 100. Among the options, only 125 divides 10000 cleanly, so p = 25 immediately.
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I like the solution - it’s helpful. I like how the solution explains how it reached the final solution even after reaching the final equation, that's a time taking bit
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