Product of the Digits

[Guest]

Hello,

I hope this isn't a silly question. I know that the formula for finding the sum of the digits (i.e., 10 + 9 + 8...+ 1) =

(n + 1)/2 x n

e.g. (10 + 1)/2 = 55

However, is there a formula for finding the product of the digits (i.e., 10 x 9 x 8... x 1)

Thanks
Malcolm

[Guest]

Unfortunately there isn't. However, it is a very useful product so it has been given its own name, it is called the factorial.
http://en.wikipedia.org/wiki/Factorial
It usually appears when you are counting permutations of objects. Although there are no simple formulas for quickly calculating it, there do exist simple approximations, see Stirling's approximation
http://en.wikipedia.org/wiki/Stirling%27s_approximation
and most calculators have a factorial button.

Hope this helped,

R. Baber.

[Guest]

Unfortunately there isn't. However, it is a very useful product so it has been given its own name, it is called the factorial.
http://en.wikipedia.org/wiki/Factorial
It usually appears when you are counting permutations of objects. Although there are no simple formulas for quickly calculating it, there do exist simple approximations, see Stirling's approximation
http://en.wikipedia.org/wiki/Stirling%27s_approximation
and most calculators have a factorial button.

Hope this helped,

R. Baber.

Yes thank you so much. My calculator does have that factorial button and Excel spreadsheets do tend do make complex calculations easier.

Cheers,
Malcolm