Nice one. No rounding either (rules are in a link above).

Here is a legal solution:

13 = 2 + 0! + 1 + 9

M57 wrote:

OK then - no extra numbers necessary..

13 = ln ((2+0)^19) RND

Why round when you can floor it.

Pratik wrote:

M57 wrote:

OK then - no extra numbers necessary..

13 = ln ((2+0)^19) RND

 

Why round when you can floor it.

watch out, the mathematicians' in the house!

15 = (2+0+1)! + 9

Still haven't found one for 14 (in order or out of order).

Found it!

14 = (2 + 0!)! - 1 + 9

Korrun wrote:

15 = (2+0+1)! + 9

Still haven't found one for 14 (in order or out of order).

Found it!

14 = (2 + 0!)! - 1 + 9

Nice!

and then -

15 = (2+0+1)!+9

16 = (2 + 0!)! + 1 + 9

Or:

15 = (2! + 0! + 1!) - 9

17 too easy for you to bother?

17 = -2 + 0 + 19

18 = -2 + 0! + 19

19 = (2x0) + 19

Nope. Just to dumb to figure it out. :)

But here is the one i've been waiting for:

20 = (20!) / (19!)

and then

21 = 2 + 0 + 19

22 = 2 + 0! + 19

Another 20 = 2^0 + 19

23 = 20^1 + sqrt 9

24 = 20 +1 + sqrt 9

And now we have the much cleaner

13 = 2 + 0! + 1 + 9 and

13 = 2^(0!+1) + 9

25 = 20 - 1 + (sqrt 9)!

26 = 20 * 1 + (sqrt 9)!

27 = 20 + 1 + (sqrt 9)!

I love how you always leave an easy one for next.

28 = 20 - 1 + 9

..and two easy ones for me!

29 = 20(1) +9

30 = 20 + 1 + 9

Korrun wrote:

I think it is because the radical symbol does not require a number to be written, but the exponent does.

Well then, that opens doors..

31 cents = (2 + 0) quarters - 19 pennies (US Currency)

32 = 2^(0! + 1 + SQRT 9)

33 = (2 + 0! + 1)! + 9

34°F = 2°F + (0 * 1 * 9)°C (scientific units of measurement)

35 oz = (2 + 0) c + 19 oz

36 points = (2 - 0!) touchdowns + (1 + 9) field goals . (US Footbal scoring)

M57 wrote:

Korrun wrote:

I think it is because the radical symbol does not require a number to be written, but the exponent does.

Well then, that opens doors..

31 cents = (2 + 0) quarters - 19 pennies (US Currency)

32 = 2^(0! + 1 + SQRT 9)

33 = (2 + 0! + 1)! + 9

34°F = 2°F + (0 * 1 * 9)°C (scientific units of measurement)

35 oz = (2 + 0) c + 19 oz

36 points = (2 - 0!) touchdowns + (1 + 9) field goals . (US Footbal scoring)

OK  - football scoring is a pretty ridiculous stretch..

We should be able to get a lot of numbers by stretching the rules..  I propose we say that doing so allows us to continue to move forward - but with the proviso that those numbers don't really count and that we are looking to improve on them.  for instance with..

36 = 9 * (0! + 2 + 1) OR

36 = 2 * 9 * (0! + 1)

which can be bettered with..

36 = 2 * (0! + 1) * 9  OR

36 = 2^(0! +1) * 9 

As a former High School/Community College math teacher I have done these games quite a bit. I do resist using the sqrt because it feels a little cheesy. M57's use of units is pretty funny/cool/imaginative though -

And, damn, 37 is not coming easy to me -

Symbols are OK, huh?

Moving on and  filling in the imaginative ones that don't count

                  9

31 = -2 +  ðšº (n-0!) 

                -1

_________________

              9 

34 =    𝚺 n

     (-2 - 0! - 1)

________________

                   9

37 = 0! +  𝚺 (n - 1)

                   2

_________________

38 = (2 + 0) * 19

39 = 20 + 19  (whew!)

40 = 2 * (0! + 19)

_________________

           12

41 =   ðšº n   -   0!

           9

_________________

           12

42 =   ðšº n   *   0!

           9

_________________

           12

43 =   ðšº n   +   0!

           9

________________

..and as long as (n = 1) is implied..

                SQRT 9

44 = (-2)  + ðšº (n + 10)

I teach 6th grade math.  I have to be imaginative.

No one is stopping me from using series?  It's a pain to notate..

Let's make this easier and use the form (𝚺, a, b, c)  where..

a = lower limit

b = upper limit

c = argument

so { ðšº, 1, 6, n+1} = 2 + 3 + 4 + 5 + 6 + 7 = 27

If only two terms are used, then it is assumed that the lower limit is 1  ..or is that stretching things too much because a number is implied? I believe it is standard nomenclature.

@Amidon37, You're gonna kick yourself.  I just stumbled upon a simpler 37 for you - It's not in order but..

37 = 19 * 2 - 0!  

45 = { ðšº, 2, 9 + 0!, n - 1 }

46 = |{ ðšº, -12, -9, n - 0! }|

47 = |{ ðšº, -9 * 0!, -1, n - 2 }|

48 = { ðšº, 1, 9, n } + 2 + 0!

49 = (9 - 2)^{(1 + 0!)}

50 = { ðšº, 9 + 0!, 12, n }

51 = { ðšº, -2, 9 +1, n } - 0!

52 = { ðšº, -2 - 0!, 9, n + 1 }

53 = { ðšº, 9 + 0!, n } + (2 - 1)

54 = { ðšº, 1 - 2, 9 + 0!, n }

55 = { ðšº, 2 * 0, 9 + 1, n }

56 = |{ ðšº, -10, 1, n }| - 2

57 = {𝚺, 0, 9 + 1, n } + 2

58 = { ðšº, 9, n + 1 } + 2 + 0!

59 = 20 * SQRT 9 - 1

60 = 20 * SQRT 9 * 1

61 = 20 * SQRT 9 + 1

62 = 21 * SQRT 9 - 0!

63 = 21 * SQRT 9 + 0!

64 = (9 - 1)^{(2 + 0)}

65 = (9 - 1)² + 0!

66 = (21 + 0!) * SQRT 9

Why @Korrun?  ..Why? ..Why?

Why did you do this to me?

67 = |{ ðšº, -9 - 2, -(0!), n}| + 1

68 = |{ ðšº, -10, SQRT 9, n - 2}|

69 = 90 - 21

70 = 9 - 2 * 10

71 = { ðšº, 9 - 1, 2n} - 0!

72 = { ðšº, 9 - 1, 2n} + 0

73 = { ðšº, 9 - 1, 2n} + 0!

Come on you guys!  I can tell you that the vast majority of 80's 90's and aughts are quite easy and don't require the use of Sigma. Uhhm, and a summing calculator  helps 

I'm missing a few in the 70's though.

I know this is about math now, but belated happy new year to you all!