Questions tagged [formation-of-numbers]
For puzzles about forming numbers using other numbers and mathematical operations. Use with [mathematics]
442
questions
19
votes
5
answers
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A riddle that has been killing me the whole day
So I'm walking around in London and found the following number riddle. The rules say, that what ever pattern you find, must be true for the rows as well as the columns. The answer in level 1 is for ...
- 278
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vote
15
answers
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Just One Line! Really? [closed]
Add ONLY ONE line (does not have to be a straight horizontal line or in other words, doesn't need to be an axis aligned to the equal sign) to make the equation below true :
EQUATION :
$5$ $+$ $5$ $+$...
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10
votes
17
answers
7k
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100 using only 5 number of digits
This is a problem from Martin Gardner.
For each digit $1\leq d\leq 9$, make 100 using exactly five number of $i$s. Any operation is allowed, brackets as well.
For $i=1,2$ I have a solution:
$$100=111-...
- 109
5
votes
2
answers
304
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 ...
- 53
2
votes
1
answer
158
views
Some Really Confusing Math
I was talking to a co-worker this morning and he stated that he was able to make both of these statements true using only $1, 3, 5,$ or $ 7$. He then proceeded to tell me:
$1 = 5$
$2 = 4 + 7$
$3 = 1$
...
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23
votes
9
answers
6k
views
Google's 20th Anniversary: Make 20 using 6 0 0 6 1 3
Belated 20th Happy Birthday to Google (600613)!
Challenge: Use 6, 0, 0, 6, 1, 3 to make the number 20.
Rules:
Use all numbers, in that exact order.
Allowed operations: +, -, x, /, sqrt, (); no ...
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7
votes
6
answers
3k
views
Use 6, 5 and 3 to make 57
Assemble a formula using the numbers $5$, $6$, and $3$ in any order to make $57$. You may use the operations $x + y$, $x - y$, $x \times y$, $x \div y$, $x!$, $\sqrt{x}$, $\sqrt[\leftroot{-2}\uproot{2}...
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14
votes
9
answers
2k
views
Use 0, 5, 7 and 1 to make 89
Assemble a formula using the numbers $5$, $0$, $1$, and $7$ in any order to make 89. You may use the operations $x + y$, $x - y$, $x \times y$, $x \div y$, $x!$, $\sqrt{x}$, $\sqrt[\leftroot{-2}\...
- 4,261
5
votes
1
answer
373
views
Palindromic number puzzle - make 505 from 20202
Can you assemble a formula using the numbers $2$, $0$, $2$, $0$, and $2$ in any order so that the results equals $505$. You may use the operations $x + y$, $x - y$, $x \times y$, $x \div y$, $x!$, $\...
- 4,261
4
votes
3
answers
1k
views
1984 - take the digits 1,9, 8 and 4 and make 123 - Part III
Part III ... Next year is the 70th anniversary of the publication of the book 1984 by George Orwell. Here is a puzzle to start the anniversary celebrations off a bit early ... I think this is the ...
- 4,261
5
votes
4
answers
228
views
Find 2018 with the least amount of numbers
Can you assemble a formula using the least amount of one digit numbers (from $0$ to $9$) so that the results equals to 2018 with the rules below?
You may use the operations $x + y$, $x - y$, $x \...
- 30.3k
11
votes
7
answers
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Fill in the boxes to get the right equation
Here is a math puzzle I had a little bit of hard time with
No computers please
There is a solution without inverting 6 to 9
- 39.2k
1
vote
4
answers
459
views
Use the digits 1, 9, 9, 8 to get 81 [closed]
Using the digits $1, 9, 9$ and $8$ in that order, and the operations $+$, $-$ and/or $\times$ in any order between pairs of digits, create an expression that equals $81$.
Normal precedence rules ...
- 23
5
votes
2
answers
254
views
Make all the ones
Given all the digits $0,\dots,9$ and using each digit exactly once,
What is the smallest possible number you can make whose digits are all $1$'s?
The only operations that are allowed are:
...
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1
vote
3
answers
305
views
1984 - take the digits 1,9, 8 and 4 and make 369
Part II... Next year is the 70th anniversary of the publication of the book 1984 by George Orwell. Here is a puzzle to start the anniversary celebrations off a bit early ...
Warm up
Can you ...
- 4,261
2
votes
2
answers
432
views
1984 - take the digits 1,9, 8 and 4 and make 246
Next year is the 70th anniversary of the publication of the book 1984 by George Orwell. Here is a puzzle to start the anniversary celebrations off a bit early ...
Warm up
Can you assemble a formula ...
- 4,261
4
votes
1
answer
185
views
A Math Puzzle with a Pattern
Inspired from a puzzle marathon, here is a math puzzle. There is a pattern with this set of numbers (not in the creation though). According to the pattern, what is the logical replacement for the ...
- 491
9
votes
1
answer
314
views
Form the biggest squaring number
You are going to start from any number with distinct digits lower than four digits (such as $a$, $ab$, $abc$) and you will apply the rule below:
Take the square any number you want in the number (you ...
- 30.3k
3
votes
2
answers
767
views
make this sum using only +
A bit of a speed question this, first correct answer gets the check. Although you are allowed to use computers, it might be quicker not to.
By placing only $+$ signs between some of the numbers on the ...
- 35.6k
33
votes
18
answers
11k
views
Use 2, 0, 1 and 8 to make 109
Assemble a formula using the numbers $2$, $0$, $1$, and $8$ in any order that equals 109. You may use the operations $x + y$, $x - y$, $x \times y$, $x \div y$, $x!$, $\sqrt{x}$, $\sqrt[\leftroot{-2}\...
- 4,261
4
votes
2
answers
974
views
Use 2, 0, 1 and 8 to make 71
Use all and only the digits $2,0,1,8$ once each to make the number $71$.
Allowed operations; anything not on this list is banned:
$+,-,\times,\div, ()$ (parentheses and/or choose function)
...
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13
votes
6
answers
3k
views
Use 2 0 1 and 8 to make 67
Use $2$ $0$ $1 $ and $8$ to make the number $67$
RULES
You must use all 4 digits.
Only the digits 2, 0, 1, and 8 can be used.
You can make multi-digit numbers out of the numbers. Examples: 20, 82, ...
- 1,881
5
votes
8
answers
619
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 ...
- 6,682
69
votes
24
answers
23k
views
Make 0 0 0 0 = 8
Can you find a way to make:
$0\ 0 \ 0 \ 0 = 8$
by adding any operations or symbols? You can use only these symbols:
$+,\ -,\ *,\ !,\ /,\ \hat\, ,\ ()$.
It is limited to this list, and ...
- 3,181
7
votes
3
answers
322
views
Is this number unique?
Inspired by Interview Question or Pathbreaking puzzle and A121808.
Start with $1$, and count the number of times $1$ occurs, and report this in the format 'number of ones:1', i.e. the next term is $...
- 35.6k
15
votes
7
answers
5k
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Make 4 4 4 4 = 30,31
Follow up question to Make 5 5 5 5 = 19
Can you find a way to make:
$4\ 4 \ 4 \ 4 = 30$
and
$4\ 4 \ 4 \ 4 = 31$
by adding any operations or symbols on the left side of the equations? You can ...
- 30.3k
10
votes
6
answers
2k
views
Maximize the number of factorials in your solution to 6 5 4 3 = 1
Using the same rules as Make 6 5 4 3 = 1, but maximize the number of factorials. You may not take the factorial of 1 or 2.
This is harder than it looks. A great answer has six factorials, an ...
- 279
11
votes
11
answers
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views
Make 6 5 4 3 = 81
Can you find a way to make:
6 5 4 3 = 81
by concatenation and/or adding any of (and only) these mathematical operators:
+
-
×
!
÷
^
standard parentheses ()
You cannot add other numbers to the ...
- 21.2k
3
votes
9
answers
1k
views
Make 6 5 4 3 = 1
Can you find a way to make:
6 5 4 3 = 1
by concatenation and/or adding any of (and only) these mathematical operators:
+
-
×
!
÷
^
standard parentheses ()
You cannot add other numbers to the ...
- 21.2k
20
votes
10
answers
14k
views
Make 5 5 5 5 = 19 [closed]
Can you find a way to make:
$5\ 5 \ 5 \ 5 = 19$
by adding any operations or symbols? You can use only these symbols:
$+,\ -,\ *,\ !,\ /,\ \hat\, ,\ ()$.
It is limited to this list, and ...
- 3,181
-5
votes
1
answer
156
views
Making 49 from 5, 1, 3, 4 [closed]
I have these numbers: 5, 1, 3, 4. There are four different ways to make 49 - what are they?
1
vote
1
answer
67
views
Find the operators
Assume you are using a basic calculator and press these numbers in order. Replace each question mark with plus, minus, multiply and divide may be used, but no sign should be used more than once. In ...
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6
votes
1
answer
134
views
The Yerata number system
There are only a few words for numbers in the Yerata1 language. Here are all of them, in random order:
imu tere nuopo rowintom
rowintom rowintom
imu tere nuopo re nuopo
rowintom re nuopo
nuobo
imu ...
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12
votes
10
answers
29k
views
Combine 3, 3, 5 & 7 to get 24
Using operators plus, minus, multiplied by and divide by, and as many brackets as you want, can you do a formula which uses 3, 3, 5 and 7 to make 24?
Each number must be used and can only be used ...
- 238
19
votes
4
answers
1k
views
5
votes
3
answers
4k
views
Use 2,3,4,5 to get 26 using only + - * /
Use 2,3,4,5 and + - * / only once each (it's not necessary to use all of them) to equal 26.
I know 2 answers, but there is a 3rd (or more) :)
- 139
4
votes
1
answer
400
views
A challenging Magic Square
Find a 3x3 Magic Square where each row, column and both diagonals result in positive number 9
You are allowed any of the 4 math operations : add, subtract, multiply or divide. NO OTHER OPERATIONS ...
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3
votes
2
answers
285
views
When is my date of birth?
___4,_4,_4
This is my real date of birth, because it looks unique, I try to do a simple operation, and I get a number 222.
In fact it is able to solved without looking at the hint, but I'm trying to ...
0
votes
2
answers
245
views
Factor the number 23 into four numbers $a + b \sqrt{2} + c \sqrt{3} + d \sqrt{6}$ [closed]
We know that $23$ is a prime number nonetheless, I'm asking to find 4 numbers $a,b,c,d > 0$ such that $23$ factors.
$$ 23 = A \times B \times C \times D \text{ with } A,B,C,D = a + b \sqrt{2} + c \...
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3
votes
10
answers
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Make numbers 1-30 using 2, 0, 1, 9
This is very similar to the 2, 0, 1, 8 problem. Just try to make all numbers 1-30 using the digits 2, 0, 1, 9.
Rules:
Use all four digits exactly once
Allowed operations: +, -, x, ÷, ! (factorial), ...
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8
votes
4
answers
4k
views
Get 59 from 1,9,4,8 in order [closed]
I’m stuck on trying get $59$ by the numbers $1,9,4,8$ in order. I have no idea if it’s possible, I made it for 1-70 just not 59.
I made it without order: $(-1+8)*9-4$
You can use not only the basic ...
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votes
2
answers
502
views
Making 30 using 3 3s [closed]
Hope that all can answer the question. It's an IQ!
How can one make 30 using 3 only three times?
- 213
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votes
4
answers
386
views
find out the missing expressions [closed]
10 10 10 10 = 1
10 10 10 10 = 2
10 10 10 10 = 3
10 10 10 10 = 4
10 10 10 10 = 5
10 10 10 10 = 6
10 10 10 10 = 7
10 10 10 10 = 8
10 10 10 10 = 9
10 10 10 10 = 10
You can only add ...
- 1
16
votes
2
answers
627
views
Ode to convergence
Taking a numeral core
(digits: a non-quad four)
digits I ordered, then
lesser I minused, till
evolve I couldn't more.
What is this unfathomably clunky poem all about?
- 77.4k
3
votes
3
answers
293
views
Puzzling Number Boxes
Found this puzzle as a translation question. The Chinese is fairly simple, it just asks to solve for the ? in the bottom right square.
The actual puzzle though, I have no clue about. Can any of you ...
- 133
-3
votes
1
answer
645
views
What is the smallest counting number you can create higher than 1? [closed]
What is the smallest integer you can create using 1,2,3,4,5,6,7,8,9 that is strictly greater than 1?
You can use any mathematics symbol.
You must use all nine numbers.
You can't use the same number ...
4
votes
2
answers
289
views
Numbers and Countries
The relations given below. According to these values, solve the last relationship.
Germany - Kenya = 7
Mexico - Brazil = 9
Turkey - Australia = 18
Norway - Ghana = 7
Korea - Japan = 1
Ethiopia - ...
7
votes
2
answers
1k
views
Pick seven numbers so that every operation gives same result
Pick seven numbers so that every operation (addition, subtraction, multiplication, but not division) gives the same result.
For subtraction, you may take the result's absolute value.
Numbers cannot ...
5
votes
3
answers
2k
views
Mathematics IQ puzzle, solving puzzle by looking at neighboring digits [closed]
Can anyone solve this puzzle? I have tried many times but I could not find any symmetry or sequence.
\begin{array} {|c|c|c|}
\hline
3&25&5\\
\hline
16&9&6\\
\hline
125&36&18\\
...
8
votes
1
answer
991
views
IBM Research Puzzle – 5-ops implementation of erasure code
I found this interesting puzzle on IBM Research Puzzling Page called Ponder This; specifically, here.
Design a storage system that encodes 24 information bits on 8 disks of 4 bits each, such that:
...
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