11
votes
11answers
1k views

A proportionality puzzle

My professor gave us this problem. In a foreign country, half of 5 is 3. Based on that same proportion, what's one-third of 10? I removed my try because it's wrong.
0
votes
1answer
20 views

Condition for L and R to make the below scenario true?

You are a given a number N. N <= 10 ^ 9 . You are given a range of numbers L and R . ...
0
votes
1answer
139 views

How many triangle can be drawn with those points? [duplicate]

There are 7 points on the circumference of a circle.How many acute triangle can be drawn with those points. please help me to solve this problem.
0
votes
1answer
119 views

Can any one help solving this puzzle of digits (Puzzle : Strike off any digit from each number in seven rows … )

Q) Strike off any digit from each number in seven rows (need not be at same place) and combine the same operations with 3 digit numbers to get the same addition. After this strike off another digit ...
2
votes
0answers
64 views

Maximizing an algebraic expression using brackets

It's a riddle of sorts: given a list of numbers $\alpha_1 \dots \alpha_n$ and operators $o_1 \dots o_{n-1}$ which can be only $\times\, \mbox{or}\, + $ if the above is a specific algebraic expression ...
7
votes
2answers
133 views

Come up with some fun “equation Limericks”

We were discussing "Limericks" in my Calculus class. Specifically, "equation Limericks". A Limerick is a poem with five lines. The first, second, and fifth lines should have nine syllables each and ...
4
votes
2answers
181 views

Logic Puzzle of Diamonds and sons

I came across a math problem and I need a solution for this. An old man has 49 diamonds. Each one has a different worth as $1, $2, $3, ….. $49. He has 7 sons and he ...
0
votes
3answers
150 views

Coded language puzzle!! [closed]

Here is a puzzle I can't crack. It goes like this: In a certain coded language MANGO=3/5 ORANGE=2/6 APPLE=1/5 Then, POTATO=?? The answer is 5/6. I would like to know to arrive at the answer.
0
votes
2answers
193 views

How to Solve an Einstein Puzzle [closed]

Ok this question is for the house team competition and this week we've been learning a lot about Einstein's Theories and calculations in maths and he's genius and we've got this maths puzzle. I know ...
5
votes
1answer
166 views

Tricky Puzzle!! Please help.

I stumbled upon a puzzle I can't crack. It goes like this: In a certain Code language: 7321=6 5342=3 8645=15 Then 9312=? The Answer is 9. But I can't seem to find the logic behind it??
3
votes
3answers
85 views

A fly on a triangle?

A fly is on the vertex of a triangle. It can move left with probability $\frac 12$ and right with probability $\frac 12$. What is the expected number of moves till it reaches its starting point? ...
4
votes
3answers
208 views

Knight on a chessboard moving from a1 to h8

I was given a puzzle to solve which goes as:- Can a knight start at square a1 of a chessboard, and go to square h8, visiting each of the remaining squares once on the way ? I reasoned that this won't ...
6
votes
2answers
203 views

General form for math puzzle solution

A math puzzle from a friend who is on a math team: The irrational number: $0.12345678910111213141516171819\dots$ has the string $314$ first occurring starting at the $17$th decimal place. When does ...
2
votes
1answer
121 views

Knight Knave puzzle with three boxes

Could you please help me with the following puzzle: Consider the following puzzle: Suppose there are two box makers: Knight and Knave. Knight always writes true statements on his box, ...
1
vote
2answers
96 views

Logic puzzle to prove which relative is male or female?

C, D, E, F, G, H, and I are the father, mother, aunt, brother, sister, wife and daughter of J, but you do not know which is which. But you know that: E and F are the same gender. C and D are of ...
2
votes
2answers
234 views

Another hat problem

A finite number of prisoners, after being given their hats (black or white), are able to see one another but themselves, and then they are ordered to jot down their guess on the color of their own ...
2
votes
1answer
95 views

Riddle - cover a $62 \times 66$ board using only $341$ straight rows of $12$ squares each

Is it possible to cover a $62 \times 66$ board using only $341$ straight rows of $12$ squares each?
1
vote
2answers
137 views

Interesting and irritating problem.

How to deal this problem. I found this problem in math competation in 2012. But, I could not solve. Could you help me... Uncle John has taken blood pressure drops for a long time according to the ...
2
votes
1answer
468 views

Spivak Chapter 2, problems 27 (and 28)

To be honest, I have no idea how to even start this problem. I'm sorry I don't have any work to show, but I'm just at a blank. Help? Chapter 2: Problem 27: "University B, once boasted 17 tenured ...
-4
votes
4answers
6k views

Puzzle of number grouping

Combine the three numbers in each group to get the same result in each of the three groups. You can use addition, subtraction, multiplication, division, and exponentiation. Here's an example of a ...
0
votes
4answers
306 views

Can you help me solve these questions related to a Logical theory?

In a group of 200 people, number of people having at least primary education (assuming - Category I): number of people having at least middle school education (Category II): number of people having ...
2
votes
1answer
674 views

In how many ways ( using only whole numbers ) can we divide 49 into 6 parts so that we can obtain any number between 1 to 49?

The series which forms the basis of all the other series is:- 1,2,4,8,16,18. Some other combinations are:- 1,2,3,7,14,22 ; 1,2,4,7,15,20 ; 1,2,4,8,13,21. However, I obtained the basic combination by ...
7
votes
4answers
274 views

A math teacher thought of a positive integer of two digits.

A math teacher thought of a positive integer of two digits. She wants her two intelligent students Hanna and Charlie determine the exact number thought. For this, Hanna is privately told how many ...
2
votes
2answers
220 views

Four men seated in a boat puzzle

I am looking for an elegant way to solve this rather simple logic puzzle using mathematical logic (statements, conjunctions, disjunctions, implications, tautologies, predicate logic and so on). I am ...
0
votes
1answer
49 views

homework cheyenne

It is a four-digit number. Its largest place value is its one place. The squares of each of its digits are less than nine. Its thousandths didgit divided by its ones digits is 50%. The sum of two pf ...
2
votes
3answers
487 views

A coin-weighing puzzle with 80 coins

In 80 coins one coin is counterfeit. What is minimum number of  weighings to find out counterfeit coin? PS: The counterfeit coin can be heavy or lighter.
2
votes
2answers
155 views

Number of songs sung.

There were 750 people when the first song was sung. After each song, 50 people are leaving the hall. How many songs are sung to make them zero? The answer is 16, I am unable to understand it. I am ...
3
votes
1answer
114 views

Square covered with tiles

A square $666\times666$ has been covered using tiles $5\times1$. A single square $1\times 1$ hasn't been covered. Find in how many places the not covered square can be.
2
votes
1answer
465 views

Sliding puzzle disjoint sets proof

Prove that the states of the 8-puzzle are divided into two disjoint sets such that any state in one of the sets is reachable from any other state in that set, but not from any state in the other ...
0
votes
2answers
312 views

Logic puzzle about travel times and distances

Each of the four person – Pawan, Rahul , SGR, Ankit –travelled at a different uniform speed out of 10 km/hr, 15 km/hr,20km/hr, and 25 km/hr for different time durations- 30 hours, 40 hours, 50 hours ...
0
votes
1answer
159 views

Diagramatic Puzzle

This is the Puzzle: and this is the hint: and the answer seems to be 000111 but I have absolutely no idea how it is done. Can anyonw help me out here? That's the puzzle. There are no other ...
0
votes
1answer
157 views

how many of relatives are female

I am working on this problem but I am not so sure my answer is right. The question is below with multiples choices but there is only is right. ...
2
votes
3answers
341 views

A tricky math problem about the difference of 2 squares

Jose is given two 2-digit numbers AB and CD where (A, B, C, and D represent unique digits) and is told to find the difference between the squares of these numbers. However, Jose has dyslexia and ...
4
votes
2answers
4k views

Puzzle - 123456789 = 100 with three operations?

Given the sequence 123456789: You can insert three operations ($+$,$-$,$\times$,$/$) into this sequence to make the equation = 100. My question is: is there a way to solve this without brute force? ...
2
votes
4answers
794 views

Show that every prime $p>3$ is either of the form $6n+1$ or of the form $6n+5$

Show that every prime $p>3$ is either of the form $6n+1$ or of the form $6n+5$, where $n=0,1,2, \dots$
1
vote
1answer
327 views

The Game of Nim

A position in Nim consists of some piles of coins. Two players alternate, with each move removing a portion of one pile. The winner is the player who takes the last coin. Suppose that the starting ...
4
votes
3answers
614 views

What is the highest number that can be got from 4383 by moving exactly 2 matches?

What is the highest number that can be got from 4383 by moving exactly 2 matches? Number 1 has got 2 matches, so I thought it will be 47831 as I remove two matches from second number (3), but it ...
3
votes
3answers
373 views

grid puzzle about combinatorics

Here is a puzzle about combinatorics. Suppose you have a square grid with $n^2$ points. You want to go from the origin $(0, 0)$ to $(n-1, n-1)$. Assuming you can only go right or up, in how many ways ...
2
votes
1answer
193 views

How do you convert this diagram into a linear system of equations/matrix form?

Question: Given is the following pipe system: the pressure in a stationary state is at every end and cross-point (with exception of $K_i, i ={1,...,4}$) equal to the average pressure of the ...
3
votes
1answer
417 views

Matrix and Binomial Coefficients

Considering the construction of a matrix as follows. The $n$th row in the matrix is filled with the coeffcients of $x^r$ in the expansion of $(1+x)^n$ from the columns $2n$ to $3n$ inclusive and ...