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'Factorial Fun' printed from https://nrich.maths.org/
Why do this problem?
The
problem does not require much knowledge but it calls for careful reasoning and accurate use of standard notation. The problem provides scaffolding steps to help the problem solver think through the ideas needed to solve the problem.
Possible approach
Ask the class to count all the factors of $n!$ for $n = 2 , 3, 4$ and $5$ and suggest that they look for the most efficient way to do this. Then suggest that this problem might help them find the best way to do it.
This is not written in to the problem itself because EVERY time we try to solve a problem, unless it is very easy, we should think about first trying simple cases.
Key questions
How do we use the fact $24=2^3 \times 3$ to deduce that $24$ has $8$ factors? (Combinatorics question)
If we find the prime factors of $n$ how do we find out how many times these prime factors are repeated in $n!$ ?
Possible support
Try the problems
Fac-finding, Powerful Factorial and
Factoring Factorials. They are all special cases of this problem.
The problem
Em'power'ed also focusses on equating the powers of prime factors.