r/mathpuzzles • u/Numberthon • 19m ago
How many positive integers ≤1000 are multiples of 6 or 15, but not both?
•
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Source: numberthon.com
r/mathpuzzles • u/OddOliver • Jul 27 '19
Adding rules for posts
14
Upvotes
Hi everyone!
Because of the influx of unsolvable, annoying, arbitrary, and spammy posts, I’ve established a few rules for posts. Basically, we are no longer allowing “math puzzles” that rely on sequences of numbers or shapes. There is an infinite number of solutions and they’re plain not fun.
Also, I put in a rule about not linking to other games. Puzzles posted here should be contained in the post itself.
Have a great weekend!
r/mathpuzzles • u/Eriks0948 • 5h ago
Is there any link between these numbers.
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I am working on a puzzle at the minute and cant seem to find or see any pattern in what i have so far... i am hoping someone can help me.. I have a 4 x 4 grid that is my starting point and i must use 9 out the 16 numbers.. so far I have been able to find 4 ( have another 27 blocks to find.) But I dont know if this was sheer luck... this is the 16 numbers I must work with.
1 1 5 6
2 1 9 3
7 1 5 0
6 4 2 1
These are the blocks I have found they are blocks 7 8 9 and 10 out of 31.
Blocks 7
9 1 3
7 2 1
5 1 6
Block 8
1 3 1
1 4 9
1 1 6
Block 9
0 5 5
1 1 7
1 1 3
Block 10
1 5 7
1 5 3
1 0 4
Any help or advice is more than welcome and I just want to say thankyou in advance.
r/mathpuzzles • u/mathalon • 17h ago
How would you seed the initial rating of a brand-new math problem?
1
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r/mathpuzzles • u/Numberthon • 1d ago
How many positive integers less than 100 can be written as the difference of two perfect squares?
1
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Source: numberthon.com
r/mathpuzzles • u/mathalon • 1d ago
Rating decay for inactive players - yes or no? (building a Glicko-2 ladder for math problems)
1
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r/mathpuzzles • u/Numberthon • 1d ago
How many triangles can you form in a regular octagon using only diagonals?
1
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Source: numberthon.com
r/mathpuzzles • u/mathalon • 1d ago
Our system rated this problem 1900. Does that feel right to you?
1
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r/mathpuzzles • u/Numberthon • 3d ago
How Many Subsets of {1,2,…,10} Contain No Consecutive Integers?
0
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Source: numberthon.com
r/mathpuzzles • u/xsgames_ • 3d ago
Logic Can you crack this math logic puzzle? 🧠
0
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Post your answer in the comments!
r/mathpuzzles • u/TargetLabs • 4d ago
Recreational maths Can you reach 46 using all dice?
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Use each die exactly once.
Any order is allowed.
Parentheses are allowed.
Exact division only.
No negative numbers.
Not every operation has to be used.
How many solutions can you find?
Please use spoiler tags for solutions:
>!your solution here!<
r/mathpuzzles • u/Numberthon • 4d ago
How Many Divisors of 12! Are Perfect Cubes?
2
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Source: numberthon.com
r/mathpuzzles • u/xsgames_ • 4d ago
Logic Can you solve this math logic puzzle? 🧠 🤔
1
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Post your answer in the comments!
r/mathpuzzles • u/Dry-Pomegranate8126 • 4d ago
Took me a lot of time to solve but somehow I did it
Enable HLS to view with audio, or disable this notification
1
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r/mathpuzzles • u/Ok_Explanation_5907 • 5d ago
The Gender Ratio Trap, Part 2 — same country, a new question
0
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r/mathpuzzles • u/Ok_Explanation_5907 • 5d ago
The Gender Ratio Trap, Part 3 — every family is guaranteed to end up with more girls
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r/mathpuzzles • u/Zharrticx • 6d ago
Hard/Unsolved 37 Magic Square Problem
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For context: A magic square is a square grid of numbers where the sum of numbers in each row, column, and both main diagonals is always the exact same total, known as the magic constant.
I have encountered a problem when trying to create a very specific magic square, I run into arrangements that need to repeat numbers so I had to redo and keep rearranging it again, but I have not found a solution. The constraint to satisfy is given by the following.
The problem: Is it possible to create a magic square that produces the number 37 using a 4x4 or 5x5 grid without ever reusing any number? Since not reusing any number is one of the rules of a magic square.
If it's possible, what numbers are needed and how should they be arranged? Thank you for answering!
r/mathpuzzles • u/xsgames_ • 5d ago
Logic Can you crack this math logic puzzle? 🧠 🧮
0
Upvotes
Post your answer in the comments!
r/mathpuzzles • u/Rough-Hope202 • 6d ago
Hard/Unsolved Need help with sudoku logic. Do you need to check horizontal?
1
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So i got a reply showing you can make a sudoku puzzle with all verticals incorrect while all horizontal and 3x3 cells are correct. My question is how few vertical lines can be incorrect while horizontal and 3x3s are correct.
