# Math a Magic trick with participation **URL:** \ **Category:** Thread Games\ **Created:** [November 2, 2020, 4:42pm UTC](https://boards.straightdope.com/t/math-a-magic-trick-with-participation/924563 "2020-11-02T16:42:00Z")\ **Posts on this page:** 10\ **Page:** 3
**Author:** ![Left\_Hand\_of\_Dorkness](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/left_hand_of_dorkness/32/7156_2.png) [@Left\_Hand\_of\_Dorkness](https://boards.straightdope.com/u/Left_Hand_of_Dorkness)\ **Post date:** [November 10, 2020, 4:27pm UTC](https://boards.straightdope.com/t/math-a-magic-trick-with-participation/924563/42 "2020-11-10T16:27:14Z")
> [@sbright33](#): > > Multiply single digits on your calculator. This is ambiguous and is not a good direction. I can fulfill it by typing “2x2”. If that’s not going to get you a workable result, you need to be clearer. ---
**Author:** ![sbright33](https://avatars.discourse-cdn.com/v4/letter/s/8e8cbc/32.png) [@sbright33](https://boards.straightdope.com/u/sbright33)\ **Post date:** [November 10, 2020, 4:48pm UTC](https://boards.straightdope.com/t/math-a-magic-trick-with-participation/924563/43 "2020-11-10T16:48:21Z")
Don’t use 0 or 5. Do it a whole bunch of times until you get to at least 8 digits in the answer. ---
**Author:** ![Left\_Hand\_of\_Dorkness](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/left_hand_of_dorkness/32/7156_2.png) [@Left\_Hand\_of\_Dorkness](https://boards.straightdope.com/u/Left_Hand_of_Dorkness)\ **Post date:** [November 10, 2020, 4:51pm UTC](https://boards.straightdope.com/t/math-a-magic-trick-with-participation/924563/44 "2020-11-10T16:51:44Z")
Step 1: Get a calculator. Step 2: Multiply single digits on the calculator together, following these three notes: Note: Do not use 0 or 5, because I hate these numbers. Note: You must use each digit at least once. Note: You cannot use the same digit twice in a row. Step 3: After you multiply by a new digit, check: is the product 8 digits long? If so, stop! If not, continue! Step 4: Type the 8-digit product as a reply to this thread, EXCEPT hide the hundreds place by replacing it with an X. So if your product is 11,111,111, you should type 11,111,x11. Step 4: MAGIC@@!!! ---
**Author:** ![sbright33](https://avatars.discourse-cdn.com/v4/letter/s/8e8cbc/32.png) [@sbright33](https://boards.straightdope.com/u/sbright33)\ **Post date:** [November 10, 2020, 4:54pm UTC](https://boards.straightdope.com/t/math-a-magic-trick-with-participation/924563/45 "2020-11-10T16:54:29Z")
Thank you! That is correct, but there is more you will see. ---
**Author:** ![Delayed\_Reflex](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/delayed_reflex/32/3172_2.png) [@Delayed\_Reflex](https://boards.straightdope.com/u/Delayed_Reflex)\ **Post date:** [November 10, 2020, 4:57pm UTC](https://boards.straightdope.com/t/math-a-magic-trick-with-participation/924563/46 "2020-11-10T16:57:33Z")
52254\_20 ---
**Author:** ![sbright33](https://avatars.discourse-cdn.com/v4/letter/s/8e8cbc/32.png) [@sbright33](https://boards.straightdope.com/u/sbright33)\ **Post date:** [November 10, 2020, 5:15pm UTC](https://boards.straightdope.com/t/math-a-magic-trick-with-participation/924563/47 "2020-11-10T17:15:00Z")
Does anyone have Excel? Using only the first 3 digits in your number above: =5\*SQRT(-COS(2))+2 ---
**Author:** ![Delayed\_Reflex](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/delayed_reflex/32/3172_2.png) [@Delayed\_Reflex](https://boards.straightdope.com/u/Delayed_Reflex)\ **Post date:** [November 10, 2020, 5:50pm UTC](https://boards.straightdope.com/t/math-a-magic-trick-with-participation/924563/48 "2020-11-10T17:50:22Z")
Neat trick - is the formula different for different numbers? I tried a second time with different numbers: 36578\_04 ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [November 10, 2020, 6:02pm UTC](https://boards.straightdope.com/t/math-a-magic-trick-with-participation/924563/49 "2020-11-10T18:02:00Z")
> [@Delayed\_Reflex](#): > > 52254\_20 > [@sbright33](#): > > Using only the first 3 digits in your number above: > =5\*SQRT(-COS(2))+2 Doesn’t match; that equals 5.22547220… ---
**Author:** ![sbright33](https://avatars.discourse-cdn.com/v4/letter/s/8e8cbc/32.png) [@sbright33](https://boards.straightdope.com/u/sbright33)\ **Post date:** [November 11, 2020, 12:21am UTC](https://boards.straightdope.com/t/math-a-magic-trick-with-participation/924563/50 "2020-11-11T00:21:20Z")
Close enough? In honor of 5 from before and your number 3. I got the answer out to 5 digits of precision before your missing digit: =-1/SIN(3+3)+33 36.578 ---
**Author:** ![sbright33](https://avatars.discourse-cdn.com/v4/letter/s/8e8cbc/32.png) [@sbright33](https://boards.straightdope.com/u/sbright33)\ **Post date:** [November 11, 2020, 12:35am UTC](https://boards.straightdope.com/t/math-a-magic-trick-with-participation/924563/51 "2020-11-11T00:35:09Z")
Just an extra 2 in there by mistake. I got the 0 right after it. [Previous page](https://boards.straightdope.com/t/math-a-magic-trick-with-participation/924563.md?page=2)