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9
votes
2answers
922 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
142 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
259 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
491 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
220 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 ...
9
votes
1answer
147 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
326 views

72 + 96 = 120, is it possible?

I came across the following riddle: How is it possible for $72+96=120$ to be correct?
3
votes
1answer
147 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
4k 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
237 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?