I did not get as many responses for this puzzle – I think people probably found it to be too easy. I was hoping that the kids would enjoy the puzzle.
The answer is 17 minutes – check out the video for the complete answer.
For those of you who are number buffs, I am assuming you know this already, but if not, I thought you might enjoy this. This was told to my brother and I as a story when my father told us about Ramanujam, and since then I have always been trying to get this number as either a car license plate or as a telephone number, though have succeeded only once so far.
The story goes like this (though I am not sure if this is 100% true) – Hardy (Ramanujam’s British colleague) came to meet Ramanujam in the hospital and told him that he bought a new car. Hardy told Ramanujam that the number of the car is 1729, when Ramanujam inquired. Ramanujam immediately told Hardy that it is a very special number. When asked why, he said that 1729 is the smallest number that can be expressed as a sum of cubes of two different positive integers in two different ways:
1x1x1 + 12x12x12 = 1729
10x10x10 + 9x9x9 = 1729
When I looked up 1729 last year on Wikipedia, I found to my surprise and excitement that if we twist the problem to not limit it to positive integers, 91 is the smallest such number – figure out how? For a more detailed version of this, look at:
http://en.wikipedia.org/wiki/1729_(number)
There are 4 people, lets call them Ramesh, Mahesh, Suresh and Jitesh. They are on a trek and it is already dark. They need to cross a bridge to reach a rest house on the other side. The bridge is flimsy and can only take two people at any given time. Also, since it is dark, they need a candle to cross the bridge and there is only one candle amongst the four of them. They also have different speeds with which they can cross the bridge – Ramesh can cross the bridge in 1 minute, Mahesh in 2 minutes, Suresh in 5 minutes and Jitesh in 10 minutes.
What is the shortest amount of time in which they can cross the bridge, and how?
Source: From a friend’s daughter (same one who gave me the 5 pirates puzzle)
Age Group: 8 years+ but good for adults as well
This was probably a more difficult problem that what I had anticipated this to be. I got much fewer responses for this compared the previous ones. This puzzle combined two different concepts – Magic Square using numbers 1-9 and the tic-tac-toe game to arrive at the answer. Here is a link to the solution:
Hope you enjoyed this, and are looking forward to the next one, which is a relatively simpler one.
This is a puzzle I discovered very recently, and really enjoyed it. Here it goes:
There are 9 cards lying face up, with numbers 1-9 written on them. Ramesh and Mahesh start playing a game – they start picking up these cards alternately, without replacement. The first person to have exactly 3 cards that add up to 15 wins the game. Ramesh starts the game by picking the first card. Does Ramesh have a winning strategy?
Age Group: I think this should be feasible for 8+ years, though not an easy one.
Source: Picked this up from a book by the name “Mathematical Puzzles, a Connessieur’s Collection” by Peter Winkler
Many people sent me the correct answers for this puzzle. Many people correctly pointed out that depending on how you interpret the behavior of the pirates, the answer could be different, and I must confess that the directions I gave were therefore not perfect.
Here is a link to the answer to the puzzle:
Hope you enjoyed the puzzle, and are looking to work on the next one!
This puzzle was shown to me by an 11 year old (Smiti Mittal) and I loved the puzzle. I have come across many puzzles of this nature, but liked this one for its simplicity and possible variations. This is from a book of puzzles used in interviews in Microsoft.
Five pirates have looted 100 gold coins. Now they have to divide their loot.These pirates are very greedy and cruel,so they want to maximize their profit and they don’t shy to kill their pirates. For distribution they decide that senior most pirate will proposes a distribution of the loot. All the pirates will vote, and if at least half accept the proposal, the loot is divided as proposed. If not, the most senior pirate will be killed, and they start over again with the next senior pirate. What solution does the most senior pirate propose? So that he can get the maximum profit, and of course live to have it!
Clarification Note: Assume that all of them are very logical, want to live and are greedy!
Target Group: Age 10 and above, good for adults as well
Variation 1: For younger kids, assume that there are only 3 pirates and then do the puzzle. This puzzle will teach kids a good way to solve a whole class of logic puzzles.
Variation 2: For age group 10 and above or anyone else who does the puzzle, repeat the same puzzle with the following change – Whenever a pirate proposes a distribution, and the group votes, they need more than half to vote in favor of the proposal to have the proposal accepted. If not the pirate who proposed is killed. What should the senior most pirate propose.
As always, answer next weekend!
Many people got the answer to the puzzle right. Very happy to see that many children tried the puzzle and got it right as well. I was particularly delighted as I have known the puzzle for a very long time and knew only one way to do it. When I gave this puzzle to a friend’s children and my own daughter, they came up with a different solution – learning never stops!
Here is the link to the solution, this time in a more friendly format, but will require Flash!
Will post the next puzzle soon!
Interesting mathematical trivia I learnt from my daughter yesterday about a special number called Kaprekar’s constant.
Take any 4 digit number with at least two distinct digits. Make the biggest and the smallest number out of these digits and find the difference between the two. Repeat the same process with the new number i.e. the difference that you just found. In a maximum of 7 iterations you will reach the number 6174, the Kaprekar’s constant!
There is a similar constant for 3 digits which is 495.
read more about it at http://en.wikipedia.org/wiki/6174
Milkman Puzzle: A milkman has three jars of the following sizes – 8 liters, 5 liters and 3 liters. The 8 liter jar is full of milk, and the 5 liter and the 3 liter jars are empty. He reaches a house and the woman of the house asks for 4 liters of milk. Unfortunately, the milkman has no 4 liter jar and has no additional markings in the existing jars to be able to figure out how to give the woman 4 liters. He also cannot borrow anything from the woman. Can you help the milkman?
Age Group: 8 years and above
Source: I do not know the source of this puzzle. My father asked me this puzzle when I was small.
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