# Help with a game puzzle (slight logic and math) **URL:** \ **Category:** The Game Room\ **Created:** [June 16, 2017, 1:18pm UTC](https://boards.straightdope.com/t/help-with-a-game-puzzle-slight-logic-and-math/789110 "2017-06-16T13:18:40Z")\ **Posts on this page:** 15\ **Page:** 1
**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:** [June 16, 2017, 1:18pm UTC](https://boards.straightdope.com/t/help-with-a-game-puzzle-slight-logic-and-math/789110/1 "2017-06-16T13:18:40Z")
Need help with a puzzle in a game. Normally I could do these ones, but it’s too early in the morning to think too hard…so here it is. Anyway…there is a code, it’s four digits. The first number is HALF of the second number, the second number is ONE more than the third number, the third number is TWO less than the fourth number, the fourth number is FOUR more than the first… …and lastly, the second number is the only number NOT a prime number. What the eff is the code? I can’t smrt right now. EDIT: Nevermind, someone on Facebook finally figured it out. After five people gave 7 wrong answers (in total, all among them), one person got it right. I’ll leave this open and unedited in case any of you want to try to figure it out and answer for yourself, though. The answer, if you’re curious, is 3657 ---
**Author:** ![Gyrate](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gyrate/32/3588_2.png) [@Gyrate](https://boards.straightdope.com/u/Gyrate)\ **Post date:** [June 16, 2017, 1:41pm UTC](https://boards.straightdope.com/t/help-with-a-game-puzzle-slight-logic-and-math/789110/2 "2017-06-16T13:41:27Z")
If the fourth number is four more than the first and both are primes (and all are single digits, obviously), that pretty much nails it down what those two are right there. The rest follow easily. ---
**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:** [June 16, 2017, 2:22pm UTC](https://boards.straightdope.com/t/help-with-a-game-puzzle-slight-logic-and-math/789110/3 "2017-06-16T14:22:09Z")
> [@Gyrate](#): > > If the fourth number is four more than the first and both are primes (and all are single digits, obviously), that pretty much nails it down what those two are right there. The rest follow easily. I got it from the first two: If the second number is twice the first, and the first is a prime, the only possible first numbers are 2 or 3. If it’s 2, then the fourth number is 6, which isn’t prime, so that’s out. So it must be 3, and the rest follows. ---
**Author:** ![pulykamell](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pulykamell/32/3166_2.png) [@pulykamell](https://boards.straightdope.com/u/pulykamell)\ **Post date:** [June 16, 2017, 4:31pm UTC](https://boards.straightdope.com/t/help-with-a-game-puzzle-slight-logic-and-math/789110/4 "2017-06-16T16:31:22Z")
I just set it up with an equation and got: 3657 With a being first digit, b being second, c being third, d being fourth: a = .5 b b = c+1 c = d-2 d= a +1 a=.5b a=.5(c+1) a=.5(d-2+1) a=.5(a+4-2+1) a=.5(a+3) a=.5a+1.5 .5a=1.5 a=3 Substitute back: 3=.5b b = 6 b=c+1 6=c+1 c=5 d=a+4 d=3+4 d=7 ---
**Author:** ![kk\_fusion](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kk_fusion/32/15276_2.png) [@kk\_fusion](https://boards.straightdope.com/u/kk_fusion)\ **Post date:** [June 16, 2017, 4:38pm UTC](https://boards.straightdope.com/t/help-with-a-game-puzzle-slight-logic-and-math/789110/5 "2017-06-16T16:38:25Z")
Without reading the thread: You want three numbers (first, third, fourth), ascending with a step of 2 between each, and all must be prime. The only prime triplet with diameter 4 is (3,5,7). From the first two clues it follows easily that the second number is 6. ---
**Author:** ![pulykamell](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pulykamell/32/3166_2.png) [@pulykamell](https://boards.straightdope.com/u/pulykamell)\ **Post date:** [June 16, 2017, 4:38pm UTC](https://boards.straightdope.com/t/help-with-a-game-puzzle-slight-logic-and-math/789110/6 "2017-06-16T16:38:39Z")
Crap, missed edit window. Above it should be: d=a+4 ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [June 16, 2017, 4:44pm UTC](https://boards.straightdope.com/t/help-with-a-game-puzzle-slight-logic-and-math/789110/7 "2017-06-16T16:44:10Z")
Am I the only one annoyed that the puzzle is overdetermined? ---
**Author:** ![pulykamell](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pulykamell/32/3166_2.png) [@pulykamell](https://boards.straightdope.com/u/pulykamell)\ **Post date:** [June 16, 2017, 4:45pm UTC](https://boards.straightdope.com/t/help-with-a-game-puzzle-slight-logic-and-math/789110/8 "2017-06-16T16:45:36Z")
Oh, I completely missed the part that said “the second number is the only number that is not a prime number.” That could speed things up exponentially–no need for algebra. The possibilities for the first number was originally just 1,2,3,4 for me, based on the second statement, but if it can only be prime, it’s just 2 and 3. Then you can just use trial and error to figure it out quite fast. If the first number is 2, then the second number must be 4, and the fourth number must be 6. But six is not prime, . So that’s out, leaving us with just “3” as the only possible answer. And, sure enough, it works. If 3 is the first number then 6 must be the second. And the fourth number must be 7 (first number plus four). So far so good. Third number is 2 less than the fourth, making it 5. Check with the other statement that second number is one more than the third number, and they agree. ---
**Author:** ![Little\_Nemo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/little_nemo/32/3120_2.png) [@Little\_Nemo](https://boards.straightdope.com/u/Little_Nemo)\ **Post date:** [June 16, 2017, 4:55pm UTC](https://boards.straightdope.com/t/help-with-a-game-puzzle-slight-logic-and-math/789110/9 "2017-06-16T16:55:56Z")
No offense to the OP but it must be really early in the morning. Knowing the second digit was twice the first and that they were a prime/non-prime pair left only two possibilities: 24 and 36. I tried them both and found 3657 was the correct one. ---
**Author:** ![DSYoungEsq](https://avatars.discourse-cdn.com/v4/letter/d/c6cbf5/32.png) [@DSYoungEsq](https://boards.straightdope.com/u/DSYoungEsq)\ **Post date:** [June 16, 2017, 7:26pm UTC](https://boards.straightdope.com/t/help-with-a-game-puzzle-slight-logic-and-math/789110/10 "2017-06-16T19:26:05Z")
> [@Chronos](#): > > Am I the only one annoyed that the puzzle is overdetermined? Very much so. Still, I did bother to solve it without reference to the prime number thing. As has been pointed out, the prime number information reduces it to simplicity, and allows for solution by trial and error in very short sequence. ---
**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:** [June 17, 2017, 6:49pm UTC](https://boards.straightdope.com/t/help-with-a-game-puzzle-slight-logic-and-math/789110/11 "2017-06-17T18:49:12Z")
> [@Chronos](#): > > Am I the only one annoyed that the puzzle is overdetermined? Well, it is a PC game rated T for teen, so I doubt it’s going to be extremely hard. The game is called Last Dream, by the way, if anyone cares… an extremely good, old school RPG. One of the best I’ve played (I just finished it yesterday). ---
**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:** [June 17, 2017, 6:50pm UTC](https://boards.straightdope.com/t/help-with-a-game-puzzle-slight-logic-and-math/789110/12 "2017-06-17T18:50:04Z")
> [@Little\_Nemo](#): > > No offense to the OP but it must be really early in the morning. > > Knowing the second digit was twice the first and that they were a prime/non-prime pair left only two possibilities: 24 and 36. I tried them both and found 3657 was the correct one. I’m math disabled. I have to numbers and math what people with dyslexia have to reading/words. There’s a name/term for it (it’s an actual thing), but I forget what it is at the moment. I didn’t even get out of long division and fractions when I was in high school. I am extremely bad at math. Extremely. ---
**Author:** ![pulykamell](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pulykamell/32/3166_2.png) [@pulykamell](https://boards.straightdope.com/u/pulykamell)\ **Post date:** [June 17, 2017, 8:28pm UTC](https://boards.straightdope.com/t/help-with-a-game-puzzle-slight-logic-and-math/789110/13 "2017-06-17T20:28:14Z")
Discalculia. ---
**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:** [June 17, 2017, 8:30pm UTC](https://boards.straightdope.com/t/help-with-a-game-puzzle-slight-logic-and-math/789110/14 "2017-06-17T20:30:58Z")
Ah, yes! That’s it. Had trouble remembering the name, but I recognized it once it was written. ---
**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:** [June 17, 2017, 8:31pm UTC](https://boards.straightdope.com/t/help-with-a-game-puzzle-slight-logic-and-math/789110/15 "2017-06-17T20:31:48Z")
Being very poor at math and numbers is my payment for being extremely good with words, language, and English.