Questions tagged [formation-of-numbers]

For puzzles about forming numbers using other numbers and mathematical operations.

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-4
votes
4answers
289 views

876925431=2016 Use the four basic operators

Use the four basic operators ×, ÷, +, − and if you want brackets to make: 8 _ 7 _ 6 _ 9 _ 2 _ 5 _ 4 _ 3 _ 1 = 2016. You can use each operator as many times as needed. Concatenation is not allowed.
6
votes
7answers
1k views

Math Challenge: Create 8

Using only $2$, $7$, and $7$ (each one must be used only once) and only using the operations $+$, $-$, $\times$, $\div$, $\textrm{^}$, and parentheses, make 8. You can also use decimals.
1
vote
0answers
138 views

Smallest Unattainable Target in Letters and Numbers (Countdown in the UK)

To cheer myself up during the twin problems of (1) underperforming sports team XXX and (2) lockdown in state YYY, neither of which shall be named, I am doing daily number puzzles based on the show ...
7
votes
1answer
153 views

There are $3$ boxes with total $27$ balls. Find minimum number of steps to get to equal balls in each box

You have $3$ boxes $A, B$ and $C$. Boxes $A$ and $B$ are empty to start with and box $C$ has $27$ balls. In "$i$-th" move you make, you must transfer exactly "$i$" balls from one ...
7
votes
1answer
429 views

Can you find the number?

There's a number with the following characteristics: The hundreds digit plus the units digit minus the tens digit equals 8. 3 times the hundreds digit plus 2 times the tens digit minus the units ...
35
votes
6answers
5k views

too easy puzzle? Try it first!

Arrange the numbers $1$ to $9$ to replace letters $A$ to $I$ so: $(A+B+C+D)-(E+F+G+H) = I$ Too easy? Too many answers? Try it first! Then explain why.
5
votes
1answer
673 views

Formula One (?) Hard Puzzle

On a website I use to go, one of the writers gave this hard puzzle: What are the meaning of those numbers given they are not Norwegian coordinates. 60.6604211,10.7210713 I have no clue how to solve ...
4
votes
1answer
119 views

Find the missing numbers in these flowers

Can you figure out the pattern and solve for the three missing numbers? All petals and centers each contain a single digit. There is a unique solution for each missing number. Hint 1: Hint 2:
8
votes
2answers
247 views

Is there a root free solution for the 6s challenge?

So the 6s challenge consist of taking a number from 0 to 10 and, using only "common" operations and the number three times, obtaining the number 6. For example: $(0!+0!+0!)! = 6$ and $(4 - (...
24
votes
21answers
3k views

When you take away two

I am an odd number. When you take away two, I become even. What am I? Edit: @hexomino got my original answer but I have come up with another valid answer. Edit 2: @QuantumTwinkie got my other ...
6
votes
8answers
2k views

Create an equation using the following numbers and mathematical symbols: 4,2,1,2,4,+, =

Create an equation using only the following numbers and mathematical symbols: $$4,2,1,2,4,+,=$$
0
votes
0answers
54 views

A Dices Probability Riddle [duplicate]

Bob (A), Steven (B) and Joe (C) were playing with dices, each one of them made his own dice and wrote a number between 1-6 on each side of his dice. After playing for a while they've noticed that : (...
13
votes
6answers
1k views

Create integers using 1, 2, 3, 4, 5, 6, 7 and +, -

There are numbers $1, 2,3,4,5,6,7$ and signs '$+$' and '$-$'. Using only these numbers and signs, you can compose expressions and calculate the sum (difference). Concatenation operation is not valid. ...
4
votes
2answers
125 views

What is a Special Prime Number™?

This is inspired by the What is a Word/Phrase™ series started by JLee with a special brand of Phrase™ and Word™ puzzles, now with numbers. If a number conforms to a special rule, I call it a Special ...
5
votes
2answers
480 views

What is a Chemical Number™?

This is inspired by the What is a Word/Phrase™ series started by JLee with a special brand of Phrase™ and Word™ puzzles, now with numbers. If a number conforms to a special rule, I call it a Chemical ...
4
votes
5answers
197 views

May Make $\frac5{2020}$ 2020

For May 2020, try to create $\dfrac{5}{2020}$ using the least possible number of integers in the set $\{1,3,4,6,7,8,9\}$. $2$, $5$ and $0$ are not allowed. Example: $$\dfrac{4+1}{3\left(673+\frac13\...
11
votes
10answers
658 views

Four fours to get $\pi$

Four fours is a famous puzzle (made trivial with logarithms). For this puzzle, we take inspiration from Glen O's challenge from a few years back. The rules here are slightly different, but the goal is ...
7
votes
2answers
931 views

Prime to number conversion

This puzzle relates to Prime to Prime: Get all first 25 Prime Numbers using up to 4 Primes and its sequel Prime to Prime Sequel Using any three of the first 4 prime numbers (2,3,5 and 7) and the ...
3
votes
1answer
78 views

Name that node #2

What is the value of the unknown node? Previous Name that node #1 (Beginner's Level Puzzle)
5
votes
1answer
75 views

Name that node #1 (Beginner's Level Puzzle)

While Puzzling.SE has some extremely clever and difficult puzzles that are being solved by people whose intellect amazes me, I wanted to make some graph puzzles that were specifically meant for ...
8
votes
0answers
311 views

I'm a number with a special product, so name me when you think you've got it

In the blocks that come before, their special product tells us more. To guess my scheme you'll need calculation, but only little tests of recreation. Each block contains atoms strong as Thor, ...
1
vote
1answer
150 views

Make the numbers 1-100 using 8 8s

Rules: Make the numbers 1-100 using eight 8s Use the operations + - * / exponentiation and ! No Rounding as in $(\sqrt{88}+8*8+8+8+8)/8= 12$ No using other digits Multi digit numbers ...
14
votes
8answers
4k views

How to get 32 by using +1 , +1 , ×3 , ×3 , ÷2 , ÷2, ^2, ^2?

How to get 32 by using +1,+1,×3,×3,÷2,÷2,^2,^2? (The last two operators are 'squaring'.)
2
votes
2answers
173 views

Make the numbers 1-100 using six 6s

Rules: Make the numbers 1-100 using six 6s Use the operations + - * / exponentiation and ! No Rounding as in $((6 - (6 + 6) / 6) + 6!!) / 6 = 9$ No using other digits Multi digit ...
6
votes
1answer
124 views

A Tribute to Countdown [closed]

Leave empty or put a multiplier, divider, adder or subtractor in the boxes: For example:
-2
votes
2answers
319 views

Make the numbers 1-50 using the digits 2, 0, 2, 0

Try to make all the numbers from 1-50 using 2, 0, 2, 0 exactly once. Rules: Use only the operations +, -, *, /, !, exponents and square root No rounding eg. ...
14
votes
2answers
660 views

Shots, shots, shots, shots!

Once in a while I go out for a drink to my favourite bar. Normally is just drink a beer, eat some snacks and have a good time with my three friends. But last night I wanted to do some shots. The ...
5
votes
1answer
385 views

Building number 81 with 1,3,3,5

You are given the numbers 1,3,3,5. Use any operation of +,−,∗,/,() to build 81 with those four numbers. You must use all four numbers exactly once. No concatenation, exponential or other symbols like ...
2
votes
5answers
568 views

Make expressions equal to 4 using exactly three 7s

Use exactly three 7s in every expression and no other digits/numbers. Choose from among addition, subtraction, division, and/or multiplication operations. You may use parentheses, brackets, and/or ...
9
votes
4answers
2k views

Four $\pi$'s to make any integer

This is like the "four four's" puzzle. The challenge is to represent any integer using $\pi$,$\pi$,$\pi$,$\pi$ (uses $\pi$ exactly $4$ times). You can use common functions on a calculator: Normal ...
7
votes
5answers
584 views

9 8 7 6 5 4 3 2 1 = 0 and 1 2 3 4 5 6 7 8 9 = 0

There are many number sequence puzzles on this site. I acknowledge them all. Martin Gardner introduced the puzzle with the 9 digit sequence with math operations, reaching 100 as below An old ...
14
votes
4answers
2k views

Emoji primes - what's the smallest positive integer this doesn't work for?

Driven by a silly conversation at work, here's the puzzle. Slack allows users to send emoji as a reaction to a message. Emoji are listed left to right in chronological order of reaction, and 'stacks' ...
14
votes
6answers
3k views

Make expressions equal to 100 using exactly seven 4s

Use exactly seven 4s in every expression and no other digits/numbers. Choose from among addition, subtraction, division, and/or multiplication operations. You may use parentheses, brackets, and/or ...
-3
votes
1answer
183 views

Make 100 with only 9 numbers [closed]

Make 100 with ONLY 9 numbers Hint 1: Hint 2: Hint 3: Hint 4:
11
votes
4answers
911 views

Making the whole set into primes

Let's say you start with a set of sequential integers starting from 2, so: $ 2, 3, 4, 5, \dots, N $ for some $ N > 2. $ The goal is to use identical basic arithmetic operations ($ +, -, \times, \...
7
votes
1answer
341 views

Building the perfect number 28 with fractions - part2

Here is a follow up of Building the perfect number 28 with fractions You are given the fractions $\frac{3}{2}, \frac{5}{2}, \frac{7}{2}, \frac{11}{2}.$ Use any operation of $+, -, *, /, ()$ to build ...
6
votes
1answer
303 views

Building the perfect number 28 with fractions

You are given the fractions $\frac{4}{3}, \frac{7}{3}, \frac{10}{3}, \frac{13}{3}.$ Use any operation of $+, -, *, /, ()$ to build 28 with those four fractions. You must use all four fractions ...
2
votes
2answers
179 views

Make numbers 1-50 using $\pi$ and its digits (but with some penalties) [closed]

In this problem, you will be allowed to use some operations and additional digits from the basic approximation of $\pi=3.14$ having some penalties, as follows: Operations: Using basic operations and ...
2
votes
1answer
152 views

Make $\pi$ using 2 0 2 0 in this order

How can you make $\pi$ using 2, 0, 2, 0 in this order? Allowed operations: +, -, x, ÷, ! (factorial), exponentiation, parentheses.
-5
votes
1answer
265 views

Make the numbers 1-50 using 2, 0, 2, 0

Make the numbers 1-50 using 2 0 2 0 in the given order. Use all four digits exactly once. Allowed operations: +, -, x, /, ! (factorial), double factorial, exponentiation, square root, parentheses. ...
2
votes
8answers
2k views

Make 28 with the numbers 2020

Try to make 28 from the numbers 2020. Allowed operations: +, -, x, ÷, ! (factorial), exponentiation, square root, squaring, parentheses.
-4
votes
3answers
235 views

Ten, nine, eight, seven, six, five, four, three, two, one

Some of us already did, and some of us are going to end the years with the word "teen" in it soon, for another 94 years. So let me ask the question: How many distinct numbers can you produce with ...
-3
votes
1answer
334 views

123456789 = 100 with three operations? [duplicate]

Given the sequence 123456789 You can insert three operations (+,-,X,/) into this sequence to make the equation = 100. Is there a way to solve this without brute force?
17
votes
2answers
1k views

A geometric sequence using one digit

Give the first few terms of a geometric[1] sequence such that: the sequence is increasing and infinite only one digit is used throughout the sequence the terms are written as base ten ...
12
votes
3answers
1k views

Fill your bucket with 2020

You are given two buckets. These buckets are a bit weird, for the only thing they can hold are numbers. One is empty, but the other one contains numbers $1,1,2$. Your goal is to get the number $2020$ ...
1
vote
4answers
250 views

Can you reach 2020?

Start with the numbers 1,2,3,4,5,6,7,8,9,10 in that order and use the four common operations (+ − × ÷) and number concatenation (ie, you may write 123 concatenating 1, 2, 3) to obtain 2020....
8
votes
9answers
3k views

Creating 123456 in the fewest number of steps

You start with the number 1. You can create a new number by applying an operation on two existing numbers (can be the same). The operations are +, - and *. What is the fewest number of steps needed to ...
8
votes
5answers
5k views

smallest number obtainable from 2020

If only the four basic operations, concatenation and parenthesis are allowed, the largest number which can be obtained from $2$ $0$ $2$ $0$ is... $2020$ :-) (If exponentials were allowed, $20^{20}$ ...
5
votes
2answers
1k views

Euler's identity

Warning: this question requires knowledge of complex numbers. An Euler's identity is an identity, in which each of the following appears once and only once: the constant $0$: neutral element for ...
-4
votes
1answer
105 views

How do I solve this puzzle?

I am trying to answer this puzzle - which of the five potential answers is correct, and why? This test comes from Metropol iq1 book

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2 3 4 5
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