Reasoning
By likely, we mean greater than 50% chance.
With one person there is a 0 percent chance that you'll have two people with the same birthday.
With two people the probability that they won't share a birthday is 364 ÷ 365. The probability that they will share a birthday is therefore 1 − (364 ÷ 365).
With three people the probability that they won't share a birthday is the same as for two people, times 363 ÷ 365. So the probability that three people will share a birthday is 1 − (364 ÷ 365) x (363 ÷ 365).
Notice that with each additional person added, the probability that they share a birthday with one of the previous persons goes up, because there are fewer "free" days remaining.
We keep adding people until the percentage is greater than 50%.
When we have 23 people the percentage is 50.729%.
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Puzzle 2
Three builders are laying a brick wall.
Freddie can lay 1,000 bricks in three hours, Jimmy can lay 1,000 bricks in two hours and Kevin can lay 1,000 bricks in six hours.
How long will it take Freddie, Jimmy, and Kevin to lay 1,000 bricks if they all work together?
1 mile = 1760 yards = 1760 x 3 feet = 1760 x 3 x 12 inches = 1760 x 3 x 12 x 25.4 millimetres = 1,609,344 mm in 1 mile.
And:
2 kilometres = 2000 metres = 2000 x 100 centimetre = 2000 x 100 x 10 millimetres = 2000 x 100 x 10 ÷ 25.4 inches = 2000 x 100 x 10 ÷ 25.4 x 16 = sixteenths of an inch ≈ 1,259,843 sixteenths of an inch in 2 kilometres.
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Puzzle 4
W B H F S K F V J P Z H S S H T J P P N W L A F P W P N T D S W S T R H S P L M V R G B I D P B D W S N R T C S R S F T D B K K F B O M F R L Z F R K Y P N J Z J S Z N M B J Q E R Z F Q Z V G Y F V P P F G F W Z W N R P L B J V R J H F K T Z U H F K Y F W J F S R S S W C Q R Q Y H R S O M W F P R Q J K H R N M B W S K B J Y D Q E T J Y P F D L R P F
