Three fours and one half of 4
Or if you mean using only fours and operation signs you develop methods like this:
42 - 4 + (4/4) = 13.
In words, four squared (16) take 4 (12), + the sum of 4/4, which is one (13).
Obviously, being an Prime number, 13 doesn't fit equally into four, so use a combination of different mathematical symbols to change four into many other numbers:
42 = 16
Square Root of four = 2
4! (four factorial) = 24
43 = 64
4/4 = 1
4 + 4 = 8
Combinations of these can be used to make the 13 you're after.
4! - 44/4 = 24 - 11 = 13
(4+4)*(4+4)=8*8=64
(44 - 4)/4
To make 15 using only four 4s, we can use basic arithmetic operations such as addition, subtraction, multiplication, and division. One way to achieve this is (4 + 4 + 4) - 4 = 12 - 4 = 8. Another way is (4 x 4) - (4 ÷ 4) = 16 - 1 = 15. In total, there are several ways to make 15 using only four 4s, and it requires creative thinking and manipulation of numbers.
44 divided by .44
The answer is 4! - [(4+4)/4]
(4x4)-(4/4) = 15
4! - 44/4 = 24 - 11 = 13
4+4+4x4 by the power of 0.
4! - sqrt 4 + 4/4
It rather depends on how many 4s there are in the stack. It's (however many 4s there are) to 25. If you had a standard pack of playing cards then there are 52 cards of which four are 4s, so your odds are 4 in 52, or 1 in 13.
(4+4)*(4+4)=8*8=64
4/.4 + 4/4 [= 10+1 = 11]
(44 - 4)/4
44/4 + 4! = 11 + (4x3x2x1) = 11 + 24 = 35
4! - sqrt(4)*sqrt(4)/4 = 23
In a standard 52 card deck, there are 13 clubs and 4 4s. However, the four of clubs is in both lists, so this represents only 16 distinct cards (the 13 clubs, and the 3 other 4s). The probability of drawing one of these 16 cards is 16/52, or 4/13.