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Archive for September, 2011

More dice rolling

Posted by Chris under MathsChallenge (4 Responds)

1. What is the average sum of the rolls when you roll two dice until the sum is 6?
e.g. (1,2),(3,5),(2,4) gives a sum of 11.
2. What is the average sum of the rolls when you roll two dice until at least one is a 6?
e.g. (1,2),(3,5),(2,6) gives a sum of 11.
3. What is the average [...]

Sum up to 6

Posted by Chris under MathsChallenge (14 Responds)

Roll a dice die until you get a 6. On average, what will the sum of the rolls be before you get the 6?
e.g. if you rolled 1,2,5,6 the sum would be 8.

Maths challenge 15

Posted by Chris under MathsChallenge (2 Responds)

Prove that for integer n > 2, that 3^n-1 doesn’t divide 5^n-1 exactly.
You’ll find http://trickofmind.com/?p=957#comments useful.

Ok, a simple problem

Posted by ragknot under Tom (6 Responds)

Did anyone learn my solution method for the Colebrook Equation?
I am talking about the simplicity of the method.
Here’s an easy one.  Find X where               X=100*Log(X).
If you learned my method, you should laugh at how easy this is.

Ooops! Posted this without a title…

Posted by Karl Sharman under MathsChallenge (5 Responds)

What squares consist of three digits 1, 4, and 9? Let’s have the first 9 or so…
The first square in the sequence is 107^2 = 11449.
If you want – have a bash at squares consisting of the three digits 2,4 and 8.

A more impossible equation? LOL

Posted by ragknot under Tom (10 Responds)

One company says this is the best version of the Colebrook Equations.  If you read my last ToM , you can do this one.  They say with this version you need to purchase their approximation method.   Assume Re =200000 and Rr=0.04 like the other one.  Figure to 15 decimals and find out “How much different is [...]

Ladies hat colours

Posted by Chris under Logic, Tom (12 Responds)

Three intelligent women, Alice, Barbara and Carol, sit down to try out a test in logical reasoning. They are arranged so that each can see each others hat, which is either red or green, but none of them can see her own hat. They are told that at least one of the hats is red. [...]

An imposible math equation?

Posted by ragknot under Tom (17 Responds)

The Colebrook-White equation was published 1937 and just about all designers of pipe say the equation is impossible to solve.  But Chris taught me a trick that most pipe companies are saying   “That can’t be right”.
They are wrong.  I call our solution a “Trick of mind” because it is an “out of the box” [...]

As simple as ABC, 123, Baby you and me… sing along if you know the words

Posted by Karl Sharman under Tom (9 Responds)

You have a whole bunch of simple objects lying in front of you – describe the missing object. Whilst you are at it – put them in the right order…
1) A cylinder
2) A Dice (or die – for the pedantic)
3) A globe of the earth
4) A wooden wedge
5) A closed doll’s house
6) A piece of [...]

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Simple Maths

Posted by Karl Sharman under Tom (6 Responds)

Make 383 out of 1,2,25,50,75,100 using +,-,*,/
That’s the question that landed on my lap a few moments ago – don’t know wether we are supposed to use all the integers, or some of them, once only, or more than once…. but hey… I’m not here to give you the answers!!! BTW you may have guessed [...]

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