Solve It 10

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$\text{If}\quad \\ f\left( 21 \right) \quad =\quad 2\\ f(83)\quad =\quad 336\\ f(91)\quad =\quad 9\\ f(65)\quad =\quad 720\\ f(95)\quad =\quad 15120\\ Then\quad find\quad the\quad value\quad of\quad f(72)\\$

This is a logical rule not a mathematical function.

154 42 65 99 48 2520 55 4562

1 solution

Tanveen Dhingra
Mar 17, 2015

The solution to this is $f(ab)\quad ={ ^{ a } }P{ _{ b } } if\quad a>b\quad and\\ \quad \quad \quad \quad \quad \quad { ^{ b } }P{ _{ a } } if \quad b>a$
Now, $f(21)={ ^{ 2 } }P{ _{ 1 } }=2\\ f(83)={ ^{ 8 } }P{ _{ 3 } }=336\\ f(91)={ ^{ 9 } }P{ _{ 1 } }=9\\ f(65)={ ^{ 6 } }P{ _{ 5 } }=720\\ f(95)={ ^{ 9 } }P{ _{ 5 } }=15120\\ { Therefore, }f(72)=\boxed { 42 }$

You need to specify that this is not a mathematical function, it is a logical rule.

Archit Boobna - 6 years, 2 months ago

What P means?

Andrea Palma - 6 years, 2 months ago

P means permutation

tanveen dhingra - 6 years, 2 months ago

Thanks a lot for clearing my doubt, mister Dhingra!

Andrea Palma - 6 years, 2 months ago

@Andrea Palma – Miss!!!...not mister!!!!..That was offending!!...I think it is quite clear from my name and the picture of my profile.

tanveen dhingra - 6 years, 2 months ago

@Tanveen Dhingra – Sorry Miss! Of course! Please accept my apologies Miss Dhingra! I have not looked at your picture, otherwise it is very clear that you are a very pretty and nice girl! Also the name doesn't tell me much because I am not acquainted with names of your wonderful country and I cannot tell by name the gender it belongs. I hope you forgive my lack of culture and attention, and I assure you I didn't want to bring any offence to such an adorable (and so smart) lady like you!

Andrea Palma - 6 years, 2 months ago

@Andrea Palma – Thank you so much!!!And its okay...i did not know you were from italy so i thought you would know the name

tanveen dhingra - 6 years, 2 months ago

Solve It 10

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