You have five coins, apparently alike, but actually of different weights. You also have a two arm scale.
Can you manage to sort the coins in ascending order, using the scale only seven times?
Bonus question: can it be done in fewer weighings?
(In reply to
yes no maybe by GOM)
I think this is asking for a method that can be sure to have the order after the weighings have occured.
Let me have a go with coins: A, B, C, D and E.
1. A vs B
2. C vs D
Lets say A is lighter than B and C is lighter than D... the order of these is arbitrary at this stage, so just change the name of the coins so this is the case.
3. B vs C
If B is lighter than C then you can put the four in order: A, B, C, D. Then finding E place is simple and if done correctly, will take less than 4 more weighings. If B is not lighter than C then more weighings are required.
4. D vs A
If D is lighter than A then the order is: C, D, A, B. Again, E can find it's place in, at most, three weighings and therefore the total is still 7. If D is not lighter than A then...
Hmm... this isn't working out. I'm gonna go off and put a bit more thought into this before I post any more.
Cheers,
Dave
re: yes no maybe
