Questions tagged [calculation-puzzle]

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

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3
votes
4answers
23k views

Find length, width and height of a cuboid [closed]

Consider a cuboid (that is, a rectangular box / rectangular parallelepiped) with the following properties: the area of its top face is $240$ cm$^2$ the area of its front face is $300$ cm$^2$ the ...
5
votes
2answers
504 views

Quick and dirty: painting a fence

There are four fences, which are geometrical identical (same heigth and same length). The following four people need the specified time to paint it: Bob needs 2 hours. Simon needs 3 hours. Tommy ...
30
votes
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 ...
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 ...
3
votes
2answers
2k views

whats the Missing Number?

In this grid of numbers, what is the missing number (in place of the question mark)? $$\begin{array}{|c|c|}\hline2&7\\\hline8&9\\\hline\end{array} \begin{array}{|c|c|}\hline0&3\\\hline5&...
12
votes
5answers
3k views

Sequence Brain Teaser: Fill the gaps to create arithmetic sequences

Fill in each blank unshaded cell in the diagram below with a positive integer less than 100, such that every consecutive group of unshaded cells within a row or column is an arithmetic sequence. This ...
7
votes
4answers
630 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 ...
14
votes
4answers
963 views

The lights in the hotel

A hotel has $n$ rooms, numbered 1, 2, 3, etc. until $n$. At the hotel reception there are $n$ buttons, one for each room, also numbered 1, 2, 3, ..., $n$. Button 1 switches the light from on to off or ...
2
votes
1answer
751 views

Can the car or the bike travel further?

There is a car and a motor-bike. The car and the bike both have an spare tire. Now, the car has a total of 5 tyres (one spare tire included) and the bike has a total of 3 tires (one spare tire ...
7
votes
2answers
1k views

Need help solving this code puzzle. Possible binary?

Me and a friend are trying to solve a series of puzzles, and this is the last one I need to solve and I'm stumped. It's a Christmas themed puzzle titled 'bLitZEN'. The only hints given are that the ...
18
votes
2answers
1k views

Ernie and the Drill Test

I dropped in to Ernie's place a while back and he asked me to stay and help calibrate his new Drilling Device. It was an impressive looking machine consisting of a large raygun-like thing mounted on ...
1
vote
4answers
659 views

Find the longest arithmetic expression with value equal to number of letters in its english representation

The expression twenty minus five has 15 letters (we ignore spaces) and also has the arithmetic value of 15. You can use standard math constants, operators and ...
6
votes
4answers
656 views

Lining Up Recruits

The good soldier Schweik had been ordered to line up a band of new recruits before their officer gave them a speech. The desired line sought to minimize the average difference in height of adjacent ...
4
votes
1answer
235 views

Not your regular Caesar Cipher$\ldots$

What in the name of the USSR does this mean?! 59 103 106 138 -1 106 138 -1 81 -1 135 81 141 103 94 135 -1 106 122 141 94 135 94 138 141 106 122 100 -1 87 125 91 94 -2 -1 91 125 122 -3 141 -1 157 ...
4
votes
2answers
747 views

How can we compute the 6 missing numbers?

There are 3 datatables. We forgot the numbers around the third square. How can we compute the 6 missing numbers?(there are question marks instead of them)
6
votes
1answer
669 views

Find out which instruction is wrong

The object of the following flow-chart is to rearrange the numbers in boxes 1, 2 and 3 in such a fashion that, at the end: ...
2
votes
2answers
231 views

The hour glasses! [duplicate]

You have two hour glasses: A seven minute one and an 11 minute one. Using just these two hour glasses, accurately time 15 minutes.
16
votes
11answers
2k views

Defuse the bomb, Mr. Rossi!

This is a very hot summer in Rome and you don't know what to do. You are the best detective in town but no crime seems to happen. You are all the day in front of your PC trying to solve some puzzles ...
8
votes
2answers
279 views

Determinine the delay on a phone call

Alice and Bob are telecommunicating in some way. When Alice speaks, it takes A seconds to reach Bob. When Bob speaks, it takes B seconds to reach Alice. Both Alice and Bob have clocks that tick at the ...
10
votes
2answers
1k views

Ernie and the Orthogonal Network

I dropped in on Ernie a while ago and he told me that there was "good news and bad news". I asked him to tell me about it and he explained as follows: "Remember my Casimir-effect electric motor and ...
35
votes
1answer
4k views

Ernie's automatic parking valet

I was helping Ernie out in his shed a while back, when his favorite screwdriver suddenly wore out. I offered to go and pick up a new one for him and Ernie thought it was a great opportunity to test-...
5
votes
3answers
968 views

Crack the Code #3

You return to the bench after cracking the last code, and you notice an envelope on the ground directly under it. You put down your envelope with the previous code and pick up the new one, ...
1
vote
1answer
581 views

How do I count Hamiltonian paths of grid?

Let's say there is a 5x5 grid with a starting position in the upper left corner, and an ending position is lower left corner. How do I count how many Hamiltonian paths there are through the grid? I ...
4
votes
1answer
957 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 ...
7
votes
3answers
1k views

How do I solve the “Between Worlds” Android puzzle game?

I've been struggling for a while with the Between Worlds Android game, and have not yet solved it. I've only noticed a couple vague properties that hold in localized cases. To operate the puzzle, ...
3
votes
2answers
4k views

Men digging holes

Suppose 9 men take 9 hours to dig 9 holes in the ground. (a) How many hours would it take 3 men to dig 3 holes? (b) How many men would it take to dig 54 holes in 54 hours?
15
votes
2answers
793 views

Santa Claus flies to the South Pole

It is a little known fact that Santa Claus is in fact a vampire. Why else would he spend so much time near the North Pole and travel only at night? Yes, he fears daylight! His problem is that ...
3
votes
2answers
517 views

Find a high-scoring 53-digit prime number chain

Let a “number chain” be a series of numbers, $n_0, n_1, ... n_{m-1}$ for some $m$, such that in base 10 the low digits of $n_i$ match high digits of $n_{(i+1)mod m}$. For example, after the number ...
7
votes
1answer
564 views

A cube puzzle (Multiple of 6)

If you have a cube, say, $3 \times 3 \times 3$, you know that mathematically it's made of $27$ ($3*3*3$) smaller cubes. Now, just remove one full line of smaller cubes (in this case, 3 smaller cubes). ...
2
votes
1answer
401 views

Make a wide tower of bridge-shapes

In this question, bridge stands for the illustrated convex quadrilateral, constructed from three equilateral triangles. Letters A, B, C, D, E are assigned to each unit length of periphery as shown in ...
1
vote
2answers
391 views

Bottle rinsing with fixed amount of wash water

Given $L$ units of wash water, we want to wash out a vessel (eg, a milk bottle, honey jar, chemistry flask...) using a series of rinses that minimize the amount of Stuff other than water remaining in ...
6
votes
3answers
506 views

Magic back yards

My back yard forms a rectangular grid of squares except some of the squares are missing as they are covered by pipes or a small tree. The layout is as follows. A 'x' indicates a square that is free ...
0
votes
3answers
43k views

Candle timing measurement [duplicate]

You are given two candles of equal size, which can burn 1 hour each. You have to measure 90 minutes with these candles. (There is no scale or clock). You are also given a lighter.
-3
votes
1answer
1k views

Can anyone explain me how to solve this problem? [closed]

Two workers A and B manufactured a batch of identical parts. A worked for 2 hours and B worked for 5 hours and they did half the job. Then they worked together for another 3 hours and they had to do (...
9
votes
3answers
2k views

Stranded Nomad Riddle

Background Story A nomad is injured in the desert. And he can't move, but fortunately an oasis is nearby, and he can stay there for enough time until rescue arrives. But the water is a magical water, ...
10
votes
3answers
2k views

The Magic Stick

Here's a relatively easy puzzle that's actually entirely my own creation. An old guru in an Asian monastery is showing his beloved student his gallery of items that he has either collected or kept ...
2
votes
1answer
396 views

What is the solution to the generic round table problem?

This question was asked about a group of people whom a king wishes to play a cruel game with. Going around in a circle, the king kills every other person. The question concerned how one could ...
9
votes
2answers
657 views

What size of puzzle is appropriate?

I am making a puzzle based on a Project Euler problem. Here is the puzzle at present: What path in the triangle below, starting from the top number with each step moving to one adjacent number in ...