Questions tagged [calculation-puzzle]

A puzzle that involves numerical calculations, such as multiplication and addition.

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63
votes
11answers
45k views

A camel transporting bananas

A somewhat well-known puzzle is described as such: You have a pile of 3,000 bananas. You wish to transport them to a place 1,000 miles away on the back of a camel; however, the camel can only carry ...
21
votes
1answer
2k views

How do I tell the children's ages?

My friend once told me a logic puzzle along the lines of: A student asks a teacher what the ages of the teacher's three kids are. The teacher said, "the product of their ages is 72, and the sum of ...
44
votes
3answers
11k views

I don't know the two numbers… but now I do

Two perfect logicians, Summer and Proctor, are told that integers $x$ and $y$ have been chosen such that $1 < x < y$ and $x+y < 100$. Summer is given the value $x+y$ and Proctor is given the ...
5
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5answers
3k views

A Set of Water Jug Challenges

You've probably heard about challenges with water jugs, so why not try a few? Use 3- and 5- liter jugs to get 4 liters. Use 5- and 7- liter jugs to get 4 liters. This one's different. How many ...
14
votes
6answers
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, ...
-3
votes
2answers
277 views

Shortest number of attempts to solve this issue [duplicate]

There are 9 identical balls but only one of them has a higher weight. You are also given a weight balance. How many attempts would you require to identify the ball with the extra weight and how?
15
votes
2answers
18k views

What's the fewest weights you need to balance any weight from 1 to 40 pounds?

Suppose you want to create a set of weights so that any object with an integer weight from 1 to 40 pounds can be balanced on a two-sided scale by placing a certain combination of these weights onto ...
17
votes
2answers
3k views

N pirates steal their share of bananas to the benefit of a monkey

The following is a type of logic / math puzzle I've yet to see on this site. I feel it belongs because the kernel of this problem can be reworked into other puzzles. $N$ pirates find themselves ...
14
votes
2answers
3k views

Product and Sum

My fellow mathematicians Paul and Sam are very fond of mathematical puzzles. One day, I came up with the idea on mathematical puzzles while three of us having lunch together. I: Hey, guys. I am ...
17
votes
2answers
12k views

Write twenty-four from four numbers

Write 24 using the four numbers 1, 3, 4, 6 and basic arithmetic. Explanations: The given are numbers, not digits, so you can't group them using decimal notation. For example, you can't create the ...
15
votes
1answer
955 views

One beer too many

You're standing outside your apartment building after a late night out, with perhaps one beer too many, and you realize you have completely forgotten the code to get in. Luckily, you're a mathematical ...
44
votes
10answers
146k views

1 2 3 4 5 6 7 8 9 = 100

The sequence of numbers $1\ 2\ 3\ 4\ 5\ 6\ 7\ 8\ 9$ has the property that you can insert mathematical operators in between the numbers from $1$ to $9$ and make the expression evaluate to 100. For ...
7
votes
4answers
379k views

Puzzle of putting numbers 1-9 in 3x3 Grid to add up to 15

In a 3x3 grid, I'd have to put numbers from 1 to 9 in a manner so that respective row, column and diagonal add up to 15. I have only been able to come up with one solution: $$\begin{array}{ccc} 6 &...
15
votes
4answers
4k views

The Mexican Standoff

There are three cowboys in a Mexican standoff against each other, named Juan, José, and Jorge. Juan is the straightest shooter in the West, and can hit his target 100% of the time. José, who has a ...
13
votes
1answer
484 views

Two honeycomb hints (yet another 'find the next number in the sequence')

Find the next number in the sequence $1,7,74,\dots$ First hint: Second hint: To clarify: the 'hints' are really clues. They are hidden, because any of the two alone could be enough to solve the ...
11
votes
3answers
2k views

A self-referring number

Find a ten-digit number with the number of zeros in it as the most significant (leftmost) digit, the number of ones as the second most significant digit etc.
4
votes
2answers
544 views

Another Way to Count Sheep At Night in Bed

I came across this puzzle: A wayfarer asks a shepherd how many sheep he has. He replies that if he numbered them two and two, or three and three, or four and four, or five and five, or six and six, ...
3
votes
2answers
2k views

A modified version of apples and oranges logic

Question: You have 3 baskets, one with apples, one with oranges and one with both apples and oranges mixed. Each basket is closed and is labeled with ‘Apples’, ‘Oranges’ and ‘Apples and Oranges’. ...
127
votes
8answers
32k views

How can 64 = 65?

Here is a interesting picture with two arrangements of four shapes. How can they make a different area with the same shapes?
30
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7answers
8k views

Aside from brute force, how can I solve this puzzle?

Once upon a time, and old lady went to sell her vast quantity of eggs at the local market. When asked how many she had, she replied: Son, I can't count past 100 but I know that: If you ...
30
votes
12answers
9k views

Correct way to add 22 to 4 to get given value

I was asked this logic puzzle in an interview. Tell me a correct way by which adding 22 to 4 will give 2. I asked interviewer what is the base of those numbers. He told that those are decimal ...
10
votes
1answer
638 views

Simple Math Problem #1

Here is a simple math problem. Can you solve it? Examples: 678+57-24*2 = 7 265+34-12*3 = 8 328+58-22*1 = 12 Problem: 541+13-21*0 = ? HINT 1: Will see if this hint makes any sense or will edit ...
19
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5answers
2k views

What is a Surpassing Phrase™?

If a phrase conforms to a certain rule, I call it a Surpassing Phrase™. Use the examples below to find the rule. Some details to save you time: 1. Font doesn't matter. 2. The number of words ...
8
votes
4answers
2k views

Travellers across a desert

This is a problem I once found in a math textbook a tutor used with me. A group of explorers is trying to get from their base camp to another camp which is eight days' walk through the desert. ...
8
votes
2answers
634 views

Four dice puzzle: 2,2,4,5

Damiano has thrown four dice and the numbers 2, 2, 4, 5 showed up on top. Damiano asks himself: What is the smallest positive integer that cannot be generated with these four numbers according to ...
7
votes
1answer
514 views

“Magic: the Gathering” Challenge #5: What if Pod was One of Us

Previous Challenge Next Challenge BACKGROUND: The usual magic rules apply here. Please be explicit in mana usage in your solution where relevant. I've tried to ensure that there are no infinite ...
5
votes
3answers
2k views

A Sand Timer Challenge

Which (if any) of these intervals is it possible to measure given two sand timers (which change from question to question)? There are no minute marks, halfway points, etc. A. 7 minutes with 4- and 5-...
1
vote
3answers
391 views

Magic: the Gathering - Challenge #6.b: It's Gonna Cost You

Previous Challenge Next Challenge Background Alright I'm going to try a more clear approach to my last attempted puzzle. Given the mana costs given below, name cards with those exact mana costs ...
50
votes
3answers
6k views

Where is Jennifer's husband?

Jennifer is 21 years older than her son Douglas. 6 years from now, Jennifer will be 5 times as old as Douglas. Question: Where is Jennifer's husband most likely to be right now?
14
votes
12answers
264k views

1 2 3 4 5 6 7 8 9 = 1

This question inspired me to write the same puzzle but instead replace the "= 100" with "= 1" with similar requirements and restrictions. What is the expression with the fewest number of operators ...
13
votes
16answers
10k views

A truly amazing way of making the number 2016

Find a mathematical expression that yields the value $2016$ while obeying the following rules: Each of the digits $1,2,3,4,5,6,7,8,9$ is used exactly once Decimal points are allowed You ...
15
votes
1answer
880 views

“Magic: the Gathering” Challenge #2: Two Peas in a Pod

Previous Challenge Next Challenge BACKGROUND: Here's a puzzle for Magic: the Gathering players out there. I feel that this puzzle is in the scope of the site, and is no different than other puzzles, ...
13
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2answers
3k views

How many distinct unsolvable Rubik's cubes exist?

I wanted to answer this question: Why can't I have only one edge piece flipped on a 3X3 Rubik's cube? by saying that it is homomorphic to the illegal state in this question: Why is a ...
10
votes
2answers
302 views

How to fill a honeymoon

        How can a honeybee visit all cells exactly once in this crescent shaped honeycomb, beginning at the bottom tip and ending at the top? The starting cell, at ...
7
votes
3answers
3k views

Where has Jones lost 1 Rs?

Jack and Jones are brothers and they both sell apples for living. Jack sells 2 apples for 1 Rs and Jones sells 3 apples for 1 Rs. They each have 30 apples. Hence, Jack earns 15 Rs a day while Jones ...
5
votes
3answers
543 views

“Magic: the Gathering” Challenge #4: Stuck in the Grenzone

Previous Challenge Next Challenge BACKGROUND: The usual magic rules apply here. Please don't post a solution that if a solution for more damage already exists. Please be explicit in mana usage ...
5
votes
2answers
814 views

“Magic: the Gathering” Challenge #3: Legends Rule

Previous Challenge Next Challenge BACKGROUND: Assume that this is a normal 20-life game of magic with no banned list (excepting cards from the 'Un' sets). If multiple solutions are tied for the ...
15
votes
1answer
1k views

Rybo switched the calculator keys!

I'm Dave. In revenge for my calculator key-switching prank, Rybo has performed a similar prank on me! My calculator has the usual number keys, and keys for the usual four arithmetic operations: ...
10
votes
2answers
523 views

Who gets more money?

There are two people eating bread. One of them has 5 loaves of bread; the other one has 3. They invited a third person to eat with them. They ate all 8 loaves of bread, and out of appreciation he gave ...
9
votes
5answers
7k views

How Will You Get 100 Fruits in Rs.100?

Source: https://www.bissoy.com/720699/ For Rs. 0.5 you get 1 Cherry. For Rs.3 you get 1 Orange. For Rs.5 you get 1 Watermelon. Your mother told you to get 100 fruits for Rs.100. ...
7
votes
1answer
1k views

Probability of Seeing a Car in 10 Minutes & 30 Minutes [closed]

On a deserted road, the probability of observing a car during a thirty-minute period is 95%. What is the chance of observing a car in a ten-minute period? Hint: To clarify the question we are saying ...
7
votes
4answers
629 views

Paint the rectangle with least movement

There is a painting brush tool that can paint a circle area of $1$ unit radius. What is the shortest paint track for painting at least a $100*100$ units rectangle area on wall? How much did the brush ...
7
votes
4answers
2k views

A truly amazing way of making every possible positive integer

This is a follow-up to "A truly amazing way of making the number 2016": For every positive integer $n$, find a mathematical expression that yields the value $n$ while obeying the following rules:...
7
votes
2answers
381 views

Fuzzy the Fuzzball

Fuzzy the fuzzball was very sad. He had lost his fuzz. Everyone knew if you lost your Fuzz you could no longer be a fuzzball. Fuzzy went to this friend Frizzy and shared his dilemma. "Don't worry, ...
7
votes
1answer
608 views

MC Frontalot 80085

MC Frontalot is a musician, and one of his songs is a word problem that seems to me like it belongs here. If you want to listen to it instead of just reading the lyrics, a quick video search of "MC ...
4
votes
3answers
1k views

The bird and the train

This question is one I found in a competitive exam paper, and has two solutions: one simple and one complex. A train starts from the east end of a 200 km long east-west track at 50 km/h. At the same ...
4
votes
4answers
564 views

Twos For Thought

How many twos do you need to get to the number $100$ exactly? Example: $22+22+22+22+2^2+2^2+2^2$ This example method uses 14 twos and is obviously not ideal. Can you find a way that uses the least ...
4
votes
1answer
955 views

Odds of duplicate birthdays

I found the following problem in an number of places online: John once bet a fellow gambler that two of the first thirty persons they met and spoke to would prove to have the same birthday. Strong ...
1
vote
7answers
873 views

Correct way to add 22 to 4 to get 70

Based on the other "Correct way to add 22 to 4" puzzles. Tell me the correct way to add 22 to 4 to get 70 As in the other puzzles, all numbers are in Base 10.
1
vote
3answers
601 views

What is the next number in the following sequence?

1, 6, 5, 3, 4, 1, 2, 2, ? Hint: the task is pattern recognition using basic mathematical operations.