Using only for 4s and any symbol how can you make 10?

Double factorial (aka semifactorial) is a mathematical operation in which one multiplies "every other" natural number up to a given number. A more precise definition is:

$$n!!=\prod \limits_{i=0}^{k}(n-2i)= n(n-2)(n-4)(n-6)...$$

Where k = (n/2) - 1 

Or read more on the "Double Factorial" Wikipedia web page :)

How about: 

4 + √4 +√4 +√4

Technically speaking you've used two's since √x = ²√x

4/4+4/4+4/4+4/4+4/4+4/4+4/4+4/4+4/4+4/4=10

Eureka!

4!!+(4+4)/4

Where "!!" stands for double factorial.

Hi Tetration

What does double factorial mean ?

How about (44 - 4)/4?

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Thanks Tetration - I have never seen that before.