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Archive for January, 2011

Going Home

Posted by Chris under Mathemagic (18 Responds)

A chauffeur always arrives at the train station at exactly five o’clock to pick up his boss and drive her home. One day his boss arrives an hour early, starts walking home, and is picked up by the chauffeur on the way out to the train station. They arrive at home twenty minutes earlier than [...]

Chicken and the Egg – It was the Egg

Posted by Karl Sharman under Tom (9 Responds)

A farmer knows that 20 of his hens, housed in 3 coops, will hatch 30 eggs in 18 days. How long will it take 30 hens, housed in 4 coops to hatch the same number of eggs?

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Nice Easy One for the Weekend

Posted by Karl Sharman under Tom (9 Responds)

A car travels at a speed of 30 mph from A to B, a distance “x” , and then return from B to A over the same distance “x” at a speed of 20 mph. What is the average speed for the total trip?

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A Barnum Puzzle

Posted by Karl Sharman under Tom (15 Responds)

This one is via PT Barnum, probably by Lloyd.
A cat and dog run a race, 100 feet straight away and back again. The dog leaps three feet at each bound and the cat but two, but then she makes three leaps to his two. Now, under those circumstances, what are the probabilities or possibilities in [...]

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10 Of the Best…?

Posted by Karl Sharman under Tom (53 Responds)

1. If 3 salesman can sell three stoves in 7 minutes, how many stoves can six salesmen sell in seventy minutes?
2. Which number when added to 5/4 gives the same result as when it is multiplied 5/4
3. Using only 3 cuts, how do you divide your round birthday cake into 8 equal slices?
4. A fish is fifteen inches long. [...]

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Firls, firls, firls

Posted by Chris under Logic (18 Responds)

I ‘m from planet X. On planet X our children are firls and moys. The probability that our firstborn child will be a firl is 3/4 After the firstborn, the probability of the next born being the same type as the previous child is 3/5.
I have three children. They are not all moys. What is [...]

Slip, sliding away

Posted by Chris under Fun Physics (18 Responds)

A smooth sphere of radius r is glued to a table top. A small mass is resting at the exact top dead centre. It is given a very small disturbance and starts to slide over the surface of the sphere. How far below the top of the sphere does the object get before separating from the sphere?
Ignore the [...]

Conditioned die

Posted by Chris under Logic, MathsChallenge (5 Responds)

I have a perfectly standard die. i.e. If I roll it I will get a 1, 2, 3, 4, 5 or 6 with equal probability.
Q1. If, out of my sight, someone rolls that die and announces that it isn’t showing a 5, what is the probability that it is showing a 6?
You and your colleague have [...]

Blue VS Red

Posted by DP under Tom (7 Responds)

Playing video games has inspired a new problem to be solved. In a 5-on-5 kill or be killed blood match with re-spawns, Blue defeats Red to 100 points.
at the end of the game, the stats come out as follows (in numerical order):
Kills – 4, 8, 11, 12, 12, 14, 16, 19, 26, 33
Deaths – 3, [...]

Karl Proposes a Probability Question. Risky!

Posted by Karl Sharman under Tom (11 Responds)

If we consider 2-digit numbers, there are exactly 18 numbers that contain the digit one: 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 31, 41, 51, 61, 71, 81, 91
As there are ninety 2-digit numbers, the probability of a 2-digit number containing a one is 18/90 = 1/5. If I have got [...]

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