Easy math puzzles
Poll
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51 members have voted
November 4th, 2025 at 9:13:06 AM
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Sorry to step on the craps puzzle, but I think we can handle two at the same time.
On Jan 1 a hospital nursery has 3 boys and an unknown number of girls. On Jan 2 a baby is born and added to the nursery. On Jan 3 a random baby is selected from the nursery and it is a boy.
What is the probability the baby born on Jan 2 was a boy?
On Jan 1 a hospital nursery has 3 boys and an unknown number of girls. On Jan 2 a baby is born and added to the nursery. On Jan 3 a random baby is selected from the nursery and it is a boy.
What is the probability the baby born on Jan 2 was a boy?
"For with much wisdom comes much sorrow." -- Ecclesiastes 1:18 (NIV)
November 4th, 2025 at 10:15:02 AM
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This comes from old racing odds used in the UK (US tracks tend to use 6/5 7/5 3/2 8/5 9/5 etc). Also we used to have Pounds, Shillings and Pence which is why some early prices were things like 100/6 100/7 100/8 and showed how many shillings you needed to put on to win £5 = 100/-. I'm guessing 1/8th (e.g. 13/8) were used as there was a half-crown (2/6) coin, and 6/4 used as it fitted into the Ev 11/10 5/4 6/4 7/4 2/1 9/4 5/2 11/4 3/1 100/30 7/2 4/1 simple pattern. (Some small greyhound tracks don't use 6/5 11/8 13/8 15/8 85/40 17/2.)Quote: Ace2Out of curiosity, why did you use 6:4 instead of 3:2 ? I’ve also seen UK sportsbooks use 6:4.Quote: charliepatrick
5/9 pays 6 to 4]
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In the old days Starting Prices were from an "average" of "leading" on-course bookmakers. This was done via a group of people going round checking the prices and, as the race started, having a "huddle". It wasn't a mathematical average but a fair price that was available on a number of good bookmakers. They, nearly always, used the nearest odds from the approved list, although in some big race tracks I've known prices such as 95/40, 35/1, 7/5 to be used.
Nowadays, at UK racetracks, Starting Price is calculated using a computer which can directly read the bookmakers prices. I'm not sure whether they still use on course bookies or have moved to include off course ones, but it uses a sample of (say) 12 and takes the median (i.e. a price available on half of the sample). This means it's a price from a specific bookie, so you now do get intermediate prices such as 7/5 8/5 11/5 16/5.
