Originally posted by gentlerock:
Hello fellow 30's!! Sorry ah, Saturday night (actually Sunday morning already), can't sleep and got nothing better to do....
There are two beakers:
Beaker 1: contains one litre of milk
Beaker 2: contains one litre of kahlua
Ready?
A "certain volume" of kahlua is taken out from Beaker 2 and poured into Beaker 1, after which it is thorougly stirred. Then the same "certain volume" of this mixture is taken out from Beaker 1 and poured back into Beaker 2.
Is there more kahlua in the milk? Or more milk in the kahlua?
at the start,
beaker 1 has 1 litre milk per 1 litre = concentration of milk = 1
beaker 2 has 1 litre kahlua per 1 litre = concentration of kahlua = 1
assume x litre of kahlua is poured from beaker 2 to beaker 1
beaker 1 now has 1+x litres
conc of milk in beaker 1 = 1/(1+x)
conc of kahlua in beaker 1 = x/(1+x)
beaker 2 now has 1-x litres
conc of milk in beaker 2 = 0
conc of kahlua in beaker 2 = 1
when x litre of mixture in beaker 1 is poured into beaker 2
both beakers now has 1 litre of mixture
conc of milk in beaker 1 = 1/(1+x) (unchanged)
conc of kahlua in beaker 1 = x/(1+x) (unchanged)
plotting graphs of y=1/(1+x) and y=x/(1+x)
1/(1+x) > x/(1+x) when x is between 0 and 1
therefore, conc of milk is always more than conc of kahlua in beaker 1 unless x = 1 litre (both will be equal in this case)
conc of milk in beaker 2 = 1/(1+x)*x = x/(1+x)
conc of kahlua in beaker 2 = x/(1+x)*x + 1-x = x²/(1+x)+ 1-x
plotting graphs of y=x/(1+x) and y=x²/(1+x)+1-x
x²/(1+x)+1-x > x/(1+x) when x is between 0 and 1
therefore, conc of kahlua is always more than conc of milk in beaker 2 unless x = 1 litre (both will be equal in this case)