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1. A ladder hangs over the side of a ship anchored in port. The bottom rung of the ladder touches the water. The distance between rungs is 30cm, and the length of the ladder is 270cm. If the tide is rising at a rate of 15cm per hour, how long will it be before the water reaches the top rung? 2. When I take five and add six, I get eleven, but when I take six and add seven, I get one. What am I? 3. A three-letter word I'm sure you know, I can be on a boat or a sleigh in the snow, I'm pals with the rain and honor a king, But my favorite use is attached to a string. What am I?

While waiting for my helicopter to arrive I decide to walk in circles around a river. I do not go over, under, or through the river, and I do not go to either end of the river, but still succeed in walking in circles around the river. The helicopter I get in has 3 rotating blades in the front and three in the back. Each front blade rotates in a direction perpendicular to the other two front blades, and each of the tail blades rotates in a direction opposite to one of the front blades. The helicopter takes me to an island, where one of my friends is waiting. We decide to go to the beach of the island and play hide and seek on the beach. The maximum distance from the ocean to the inland forest is only 1.5 times the width of either of our bodies, and that is what we will define as the beach for our game of hide and seek. I give my friend some time to find a hiding spot and then go looking for her. I go all the way around the beach, but still do not find my friend, even though I have excellent vision, my friend never went inland, the island is well lit, and my friend stands out really well from the beach. Eventually I give up, and my friend wins the game of hide and seek. Every point on the surface of my planet is moving at about the same rate relative to the center of my planet. The surface of my planet has two great circles, one of maximum brightness, and one of minimum brightness. The great circle of maximum brightness is the hottest part of the surface of my planet, and the great circle of minimum brightness is the coldest part of the surface of my planet. What is the thing that is unusual about the environment I live in that explains all the above clues? Every above clue can be explained by one unusual thing about my environment.

1. There are 500 coffins and 500 men who need them. The undertaker asks the first man to go to every coffin and open them. Then he tells the second man to go to everyone and close it. The third one goes to every third coffin and so on. How many are open? 2. In a bicycle race, the man who came two places in front of the last man finished one ahead of the man who came fifth. How many contestants were there? 3. You have 14 brown socks, 14 blue socks and 14 black socks in your sock drawer. How many socks must you remove (without looking to be sure) to have a matched pair? 4. Joe has ten coins totaling $1.19. From these coins, he cannot make exact change for a dollar, half-dollar, quarter, dime, or nickel. 5. There are 12 kids in a classroom. 6 kids are wearing socks and 4 are wearing shoes. 3 kids are wearing both. How many are bare feet?

5. From The New York Times, Science Times, D5, April 10, 2001:“Three players enter a room and a red or blue hat is placed on each person’s head.The color of each hat is determined by [an independent] coin toss. No communicationof any sort is allowed, except for an initial strategy session before the game begins.Once they have had a chance to look at the other hats [but not their own], theplayers must simultaneously guess the color of their own hats or pass. The puzzleis to find a group strategy that maximizes the probability that at least one personguesses correctly and no-one guesses incorrectly.”The naive strategy would be for the group to agree that one person should guess and theothers pass. This would have probability 1/2 of success. Find a strategy with a greater chancefor success.For a different problem, allow every one of n people to place an even bet on the color of hishat. The bet can either be on red or on blue and the amount of each bet is arbitrary. The groupwins if their combined wins are strictly greater than their losses. Find, with proof, a strategywith maximal winning probability.

You are seated at a table across from your archenemy. Between you are two small plates with 5 skittles on each (red, orange, yellow, green, and blue). Though the plates look identical, the one in front of you has had 3 of its skittles dipped in poison: just enough so that eating 2 poisoned skittles will kill you. The plate in front of your archenemy has only had 2 of its skittles poisoned. You choose which plate to eat from, your archenemy will eat the other. 1) Would you rather eat 2 skittles from your plate, or 3 skittles from your archenemy's plate? 2) What are the odds that you both survive? 3) What are the odds that you are both killed from the poison? 4) What are the odds that neither of you eat any poisoned skittles at all? 5) What are the odds that you will survive and your archenemy will be killed? [EDIT] Remember, eating 1 poisoned skittle does nothing, but eating 2 kills a person!

Put a smiley face like this: to participate in a pi lottery of 30 pi. You can put any smiley you want, and you can put 1-5 smileys. Let's start! P.S. The lottery registration ends March 1. Lottery Results will be posted soon after that.

These questions use a standard deck of 52 playing cards with no jokers or wild cards. #1) If you randomly deal 2 cards, what is the probability that both cards are aces? #2) If you randomly deal 2 cards, what is the probability that the cards are an ace and king of the same suit? #3) If you randomly deal 13 cards, what is the probability that all 13 cards are the same suit?

Complete in the next 48 hours for 3 pi. (Please keep track of your pi, as it has gotten harder.) https://docs.google.com/forms/d/1REQ3e8j_O_nTLQC1FtIwwVTp-bcnE8oIHampaJG64Ck

Let x be a variable that can take on the value of any ordinal number. The ordinal numbers are 0, 1, 2, 3, … What is the smallest ordinal number x for which 1+x=x? The first person with a correct answer gets a trophy of their choice.

https://www.chess.com/club/matches/math-and-chess-club/1097654/games Hey there. Want to have a tough opponent and battle it out until the end? This is where you belong. Come and join us! Yes, I'm talking to you.

There are 8 sisters who decided to do things since they were very bored. Here is what the sisters were doing: The first one was doing laundry. The second one was sleeping. The third one was playing chess. The fourth one was cooking food. The fifth one was texting. The sixth one was doing homework. The seventh one was reading. Question: What was the 8th sister doing?

These are not math-related, but still a challenge for your brain. 1. No legs have I to dance, No lungs have I to breathe, No life have I to live or die And yet I do all three. What am I? 2. I can bring tears to your eyes; resurrect the dead, make you smile, and reverse time. I form in an instant but I last a lifetime. What am I? 3. He has one and a person has two, a citizen has three and a human being has four, a personality has five and an inhabitant of earth has six. What am I? 4. What english word retains the same pronunciation, even after you take away four of its five letters? Challenge (4 pi) 5. I dig out tiny caves, and store gold and silver in them. I also build bridges of silver and make crowns of gold. They are the smallest you could imagine. Sooner or later everybody needs my help, yet many people are afraid to let me help them. Who am I?

The forum ends on 2/14/20. Hardest (Made by yourself) Math Problem Wins 15 pi!

Here, you can talk with each other and challenge each other to games.

I=1 Am I correct? V=5 X=10 L=50 C=100 D=500 M=1000

Give a hard math question,whoever gives the hardest wins 1 pi.

What is a complex number? Well, to get into that, we need to first understand what an imaginary number is. Okay, so you probably know that you can always have a square root of a positive number right? But what is the square root of a negative number??? For example, what in the world is sqrt(-1)??? This really doesn't make sense since for any real number n, n^2 = |n^2|, and since the absolute value of any real number is always positive, and 0^2 = 0. However, in 1637, Reni Descartes made an idea of an imaginary number, and let the value of sqrt(-1) equal to a variable i. Today, we call i an "imaginary number". A complex number is any number that can be expressed the form x + yi. In this forum, we will test your knowledge about complex numbers and see how good you are at it. 1) Let the value of (5i + 3)(2i + 4) be expressed in the form x + yi where x and y are real numbers. 1a) What is x? 1b) What is y? 2) Let the value of (2i + 3)/(3i + 4) be expressed in the form a + bi where a and b are real number. 2a) Find a. 2b) Find b. BONUS: 3) Let there be quadratic be expressed in the form ax^2 + bx + c = 0. 3a) What are the conditions of a and b such that the two roots of the quadratic are real? 3b) What are the conditions of a and b such that the two roots of the quadratic are imaginary?

Post one chess puzzle ONLY.Can be opening,middle game or endgame.

Try to solve as many of these math problems if you can. Good Luck! 1) What is the value of (1/2) * (2/3) * (3/4) * (4/5) * (5/6) * ... *(197/198) * (198/199) * (199/200)? 2) Compute 1/(1*2) + 1/(2*3) + 1/(3*4) + ... + 1/(999*1000). 3) Find the value of (1/(sqrt(1) + sqrt(2)) + (1/(sqrt(2) + sqrt(3)) + (1/(sqrt(3) + sqrt(4)) + ... + (1/(sqrt(399) + sqrt(400)). 4) Let there exist a number x such that x^0 + x^1 + x^2 + x^3 + x^4 + ... = 2020. If x can be expressed in the form p/q where p and q are relatively prime, what is p + q? 5) Compute (1/2^1) + (2/2^2) + (3/2^3) + (4/2^4) + ...

There are some great math posts by @SciFiChess, @createsure, and more. If your problem is not too easy (like 2 + 2), then you can offer 2 to 3 pi per problem posted. If you are new, https://www.chess.com/news/view/currency-system-is-finally-here That's the pi system for you.