# Do this math problem in your head. **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [October 28, 2008, 2:08pm UTC](https://boards.straightdope.com/t/do-this-math-problem-in-your-head/469932 "2008-10-28T14:08:40Z")\ **Posts on this page:** 20\ **Page:** 5
**Author:** ![Kythereia](https://avatars.discourse-cdn.com/v4/letter/k/e8c25b/32.png) [@Kythereia](https://boards.straightdope.com/u/Kythereia)\ **Post date:** [October 28, 2008, 6:07pm UTC](https://boards.straightdope.com/t/do-this-math-problem-in-your-head/469932/81 "2008-10-28T18:07:29Z")
1. This is going to end up being the wrong answer, right? ---
**Author:** ![IvoryTowerDenizen](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ivorytowerdenizen/32/17937_2.png) [@IvoryTowerDenizen](https://boards.straightdope.com/u/IvoryTowerDenizen)\ **Post date:** [October 28, 2008, 6:24pm UTC](https://boards.straightdope.com/t/do-this-math-problem-in-your-head/469932/82 "2008-10-28T18:24:10Z")
> [@Agent\_Foxtrot](#): > > I’m not sure I believe most of these 4100’s. :rolleyes: Why the doubt? It’s not hard math, it just requires you to be careful. ---
**Author:** ![peedin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/peedin/32/14095_2.png) [@peedin](https://boards.straightdope.com/u/peedin)\ **Post date:** [October 28, 2008, 6:42pm UTC](https://boards.straightdope.com/t/do-this-math-problem-in-your-head/469932/83 "2008-10-28T18:42:50Z")
4080 ---
**Author:** ![The\_Tof](https://avatars.discourse-cdn.com/v4/letter/t/cdc98d/32.png) [@The\_Tof](https://boards.straightdope.com/u/The_Tof)\ **Post date:** [October 28, 2008, 6:55pm UTC](https://boards.straightdope.com/t/do-this-math-problem-in-your-head/469932/84 "2008-10-28T18:55:40Z")
4100 ---
**Author:** ![Idle\_Thoughts](https://avatars.discourse-cdn.com/v4/letter/i/838e76/32.png) [@Idle\_Thoughts](https://boards.straightdope.com/u/Idle_Thoughts)\ **Post date:** [October 28, 2008, 7:08pm UTC](https://boards.straightdope.com/t/do-this-math-problem-in-your-head/469932/85 "2008-10-28T19:08:35Z")
> [@peedin](#): > > 4080 :dubious: So, so far, about 8 or 9 “5000s”. That’s about average for a topic. 🙂 That average would go wayyyyyyyyyyyyyy higher had it actually be spoken aloud (I think). ---
**Author:** ![NicePete](https://avatars.discourse-cdn.com/v4/letter/n/ee7513/32.png) [@NicePete](https://boards.straightdope.com/u/NicePete)\ **Post date:** [October 28, 2008, 7:16pm UTC](https://boards.straightdope.com/t/do-this-math-problem-in-your-head/469932/86 "2008-10-28T19:16:42Z")
4100 ---
**Author:** ![FlyingCowOfDoom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/flyingcowofdoom/32/21776_2.png) [@FlyingCowOfDoom](https://boards.straightdope.com/u/FlyingCowOfDoom)\ **Post date:** [October 28, 2008, 7:26pm UTC](https://boards.straightdope.com/t/do-this-math-problem-in-your-head/469932/87 "2008-10-28T19:26:00Z")
$Texas –FCOD ---
**Author:** ![Shark](https://avatars.discourse-cdn.com/v4/letter/s/73ab20/32.png) [@Shark](https://boards.straightdope.com/u/Shark)\ **Post date:** [October 28, 2008, 7:26pm UTC](https://boards.straightdope.com/t/do-this-math-problem-in-your-head/469932/88 "2008-10-28T19:26:51Z")
4100 What do I win? ---
**Author:** ![CAT\_1](https://avatars.discourse-cdn.com/v4/letter/c/9dc877/32.png) [@CAT\_1](https://boards.straightdope.com/u/CAT_1)\ **Post date:** [October 28, 2008, 7:43pm UTC](https://boards.straightdope.com/t/do-this-math-problem-in-your-head/469932/89 "2008-10-28T19:43:16Z")
4100 But I admit I have seen this before. I was almost stumped the first time, but knew there must be a trick, so said it all outloud very carefully when adding. ---
**Author:** ![BetsQ](https://avatars.discourse-cdn.com/v4/letter/b/fbc32d/32.png) [@BetsQ](https://boards.straightdope.com/u/BetsQ)\ **Post date:** [October 28, 2008, 7:45pm UTC](https://boards.straightdope.com/t/do-this-math-problem-in-your-head/469932/90 "2008-10-28T19:45:07Z")
4100 ---
**Author:** ![Ponch8](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ponch8/32/9883_2.png) [@Ponch8](https://boards.straightdope.com/u/Ponch8)\ **Post date:** [October 28, 2008, 7:46pm UTC](https://boards.straightdope.com/t/do-this-math-problem-in-your-head/469932/91 "2008-10-28T19:46:36Z")
5000 ETA: D’oh! ---
**Author:** ![MentalGuy](https://avatars.discourse-cdn.com/v4/letter/m/439d5e/32.png) [@MentalGuy](https://boards.straightdope.com/u/MentalGuy)\ **Post date:** [October 28, 2008, 7:59pm UTC](https://boards.straightdope.com/t/do-this-math-problem-in-your-head/469932/92 "2008-10-28T19:59:35Z")
4100 ---
**Author:** ![iamthewalrus\_3](https://avatars.discourse-cdn.com/v4/letter/i/258eb7/32.png) [@iamthewalrus\_3](https://boards.straightdope.com/u/iamthewalrus_3)\ **Post date:** [October 28, 2008, 8:33pm UTC](https://boards.straightdope.com/t/do-this-math-problem-in-your-head/469932/93 "2008-10-28T20:33:26Z")
4100, unless I miscounted. ETA: I was more careful than I might normally be, since I knew there must be some trick. Part of my brain did jump to 5000, but then I read the numbers again. ---
**Author:** ![postcards](https://avatars.discourse-cdn.com/v4/letter/p/8e8cbc/32.png) [@postcards](https://boards.straightdope.com/u/postcards)\ **Post date:** [October 28, 2008, 8:36pm UTC](https://boards.straightdope.com/t/do-this-math-problem-in-your-head/469932/94 "2008-10-28T20:36:57Z")
5000 ---
**Author:** ![gigi](https://avatars.discourse-cdn.com/v4/letter/g/a587f6/32.png) [@gigi](https://boards.straightdope.com/u/gigi)\ **Post date:** [October 28, 2008, 8:47pm UTC](https://boards.straightdope.com/t/do-this-math-problem-in-your-head/469932/95 "2008-10-28T20:47:12Z")
4100, but 5000 did float through my head until I figured that was probably the common goof. (Unless 4100 is also wrong!) ---
**Author:** ![Freudian\_Slit](https://avatars.discourse-cdn.com/v4/letter/f/5daacb/32.png) [@Freudian\_Slit](https://boards.straightdope.com/u/Freudian_Slit)\ **Post date:** [October 28, 2008, 8:53pm UTC](https://boards.straightdope.com/t/do-this-math-problem-in-your-head/469932/96 "2008-10-28T20:53:17Z")
> [@Agent\_Foxtrot](#): > > I’m not sure I believe most of these 4100’s. :rolleyes: I would have said 5,000 if I hadn’t already seen this problem before. ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [October 28, 2008, 8:53pm UTC](https://boards.straightdope.com/t/do-this-math-problem-in-your-head/469932/97 "2008-10-28T20:53:52Z")
1. But no doubt there’s some kind of trickery involved and that’s wrong… ---
**Author:** ![Hazle\_Weatherfield](https://avatars.discourse-cdn.com/v4/letter/h/e9bcb4/32.png) [@Hazle\_Weatherfield](https://boards.straightdope.com/u/Hazle_Weatherfield)\ **Post date:** [October 28, 2008, 9:06pm UTC](https://boards.straightdope.com/t/do-this-math-problem-in-your-head/469932/98 "2008-10-28T21:06:27Z")
5000 ---
**Author:** ![vintageloveletter](https://avatars.discourse-cdn.com/v4/letter/v/8e8cbc/32.png) [@vintageloveletter](https://boards.straightdope.com/u/vintageloveletter)\ **Post date:** [October 28, 2008, 9:06pm UTC](https://boards.straightdope.com/t/do-this-math-problem-in-your-head/469932/99 "2008-10-28T21:06:55Z")
4,100 ---
**Author:** ![Enginerd](https://avatars.discourse-cdn.com/v4/letter/e/bcef8e/32.png) [@Enginerd](https://boards.straightdope.com/u/Enginerd)\ **Post date:** [October 28, 2008, 9:08pm UTC](https://boards.straightdope.com/t/do-this-math-problem-in-your-head/469932/100 "2008-10-28T21:08:20Z")
1. Don’t worry, though - I don’t design anything you might drive over. [Previous page](https://boards.straightdope.com/t/do-this-math-problem-in-your-head/469932.md?page=4) [Next page](https://boards.straightdope.com/t/do-this-math-problem-in-your-head/469932.md?page=6)