Maths problems (interesting ones)

[Denman]

just going to post some random puzzles here, to keep people interested in maths!

Post your answers here, i might make it a quiz or something !
puzzle 1 )
4 astronauts must get from their pod to their ship in 12 mins

they have 1 oxygen tank which can support up to two people at a time

all astronauts travel at different speeds and if two astronauts share the oxygen take, they travel at the speed of the slowest astronaut
The speeds at which they can travel are as follows:

A:1
B:2
C:4
D:5

if A and D go and A returns, this is (Total 6 mins), then A and C go and A returns (Total 11 mins) then A and B go the total is 13 mins. How can it be done?


Puzzle 2)
2 fathers and 2 sons went into a restaurant and ordered 3 whole pies, and they ate 1 whole pie each (no! 1 whole pie, not pi, because 1 pi radian is only half of a pie). How come?

Puzzle 3)
How can you get 4 liters of water EXACTLY from using an unlimited supply of water and a 5 liter and 3 liter bucket???

More to follow if there is any interest......