Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [number-property]

Puzzles that use number properties such as even and odd, multiples of numbers, part of a well-known sequence (i.e. Fibonacci) or theorem (Pythagorean relations) or others in part of the method to solve the question.

-5
votes
3answers
141 views

Circular Logic - It just doesn't add up [closed]

It seems one of these numbers just doesn't belong... Can you tell us why??
13
votes
3answers
473 views

Hiker's Cabin Mystery | Pt. II

See Part I | See Part III Nice one, @GarethMcCaughan! Finally, you've gotten into his computer using the password you managed to decode from his clues... but there's another issue! There is a ...
10
votes
1answer
564 views

I'm thinking of a number

The unusual thing about this number is that the most common phrases that use it are wrong. That is, while someone may often say there are X As in a B, the actual number is not X. What number am I ...
9
votes
1answer
167 views

What's the significance of this pattern?

Note, this is my first submission, let me know if I broke the rules. What is the significance of the following sequence of # signs? ...
4
votes
5answers
421 views

Haters will say 28 June

Find the next number in this sequence: $4,3,7,5,10,15,?$ Think outside the frustum here. Hint 1: Hint 2:
8
votes
8answers
1k views

What mysterious whole number am I?

From my second point of view I copy that amount of first. I am the dominant side of two but for many I'm the worst. I'll be tricky to find but today might be your day, after all my neighbour is 2/3 of ...
9
votes
2answers
1k views

Ten-digit number that satisfy divisibilty rules for 2,3,4,5,6,7,8,9,10&11

Question: Arrange the digits 1,2,3,4,5,6,7,8,9,0 to make a ten-digit Number that satisfies all of the divisibility rules for 2,3,4,5,6,8,9,10,&11. BONUS: make the number also divisible by 7
5
votes
2answers
256 views

Using 20, 17, 16, 8, 7 to make 9

You can use $+, -, \times, $ or $/$ (namely $\div$). Use all five numbers (20, 17, 16, 8, and 7) only once to make $9$. From what I've been told there are $4$ answers. The only one I've been able ...
8
votes
4answers
379 views

A “Find the Path” Puzzle

I invented a puzzle, inspired by Simon Tatham's Portable Puzzle Collection. Is there anything that it could improve on? Was it too easy, or was it too hard? Anything I could add? What must I call it? ...
6
votes
8answers
518 views

Make $1,\dots,15$ using $3, 9, 9, 9$

This was inspired by many puzzles that use three/four numbers to create other numbers. I chose these numbers in particular because of this post. Can you find a way to make all the natural numbers ...
8
votes
2answers
229 views

Half and Double Value

A 3 year old child tried to input or copy a number (written on the paper) to a calculator but he messed up with the digit places. All the digits are there but the value of the number he inputed ...
11
votes
1answer
180 views

What is a Voluminous Number™?

In the spirit of the What is a Word™/Phrase™ series started by JLee, a special brand of Phrase™ and Word™ puzzles. If a number conforms to a special rule, I call it a Voluminous Number™. Use the ...
2
votes
3answers
389 views

72 + 96 = 120, is it possible?

I came across the following riddle: How is it possible for $72+96=120$ to be correct?
4
votes
1answer
204 views

systematic number removal [duplicate]

The whole, natural numbers 1 through 50 are written on a board. The following operation is performed 49 times: select any two of the numbers on the board and write the absolute value of their ...
17
votes
3answers
5k views

Which two students spoke wrongly? [duplicate]

A teacher wrote a large number on the board and asked the students to tell about the divisors of the number one by one. The 1st student said, "The number is divisible by 2." The 2nd student said, "...
6
votes
1answer
238 views

What do numbers have?

Numbers 0 through 9 each have a number of something. 0 has 6. 1 has 2. 2 has 5. 3 has 5. 4 has 4. How many do 5, 6, 7, 8 and 9 have?