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

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589
7

Using only four 4's and any symbol, how can you make 10?

Jan 9, 2015

### Best Answer

#6
+808
+5

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 :)

Jan 10, 2015

### 7+0 Answers

#1
+808
+5

How about:

4 + √4 +√4 +√4

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

Jan 9, 2015
#2
+100813
+5

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

Jan 9, 2015
#3
+808
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Eureka!

4!!+(4+4)/4

Where "!!" stands for double factorial.

Jan 9, 2015
#4
+100813
0

Hi Tetration

What does double factorial mean ?

Jan 10, 2015
#5
+27837
+5

How about (44 - 4)/4?

.

Jan 10, 2015
#6
+808
+5
Best Answer

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 :)

Tetration Jan 10, 2015
#7
+100813
0

Thanks Tetration - I have never seen that before.

Jan 11, 2015