4
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A sixth riddle!

There's a function just

(reserved)

for me

though you need three

of me to complete it.

Don't simplify

(me)

when the top's much larger;

I'll explode

before you know it.

What am I?

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6
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I think it may be (only may be , not sure!!!)

Combinatorics (combinations)

There's a function just (reserved) for me

though you need three of me to complete it.

Expression : $^nC_r $ - three symbols required to complete the expression, also $^nC_r = \frac{n!}{r!(n-r)!}$ - three 'factorial' terms

Don' t simplify when the top's much larger

Evaluating $^nC_r$ becomes tedious, if $n$ is large, (provided $r$ is not very large or small ) . $$$$ For e.g, $^{520}C_{14} = 1016179801403563036214357760$

I'll explode before you know it

May be the same as above or combinatorial explosion https://en.wikipedia.org/wiki/Combinatorial_explosion

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  • $\begingroup$ Thank you! Is it really correct? $\endgroup$ – Ak19 May 20 at 6:35
  • 1
    $\begingroup$ Yep! Note that the function was originally a reference to the hypergeometric distribution with parameters given by $\sf{Hy(x\mid N,d,n)}$ and density function $$p(x)=\frac{\binom dx \binom{N-d}{n-x}}{\binom Nn}$$ and as you can see, it is made up of three combinations. Great job! $\endgroup$ – TheSimpliFire May 20 at 6:38
  • $\begingroup$ Thanks a lot!!! $\endgroup$ – Ak19 May 20 at 6:38
1
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First Attempt (possibility to be correct: 20%)

cone?

There's a function just

(reserved)

for me

Volume of a cone : $pi*r^2*h/3$

though you need three

of me to complete it.

denominator = $3$, complete: without it?

Don't simplify

(me)

when the top's much larger;

I'll explode

pi is just sooooo long... when simplified...

before you know it.
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