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You are given 2 eggs.

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AB Editor | 15:57 Fri 04th Jun 2010 | Riddles
24 Answers
You are given 2 eggs.

You have access to a 100-story building.

Eggs can be very hard or very fragile means it may break if dropped from the first floor or may not even break if dropped from 100th floor.

Both eggs are identical.

You need to figure out the highest floor of a 100-story building an egg can be dropped without breaking.

The question is how many drops you need to make. You are allowed to break 2 eggs in the process.
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Drop one from floor 50. If it breaks then answer lies between 1 and 50. With the other egg try floor 1; if it survives try floor 2; if it survives try floor 3. Coninue until it breaks. You then know thehighest floor it can be dropped from
To be continued when i've worked out the rest
If it didn't break from 50 then you still have 2 eggs. Go half way up the rest of the building to floor 75. If it breaks then answer lies between 50 and 75. So try 51, 52 etc until it breaks

If it didn't break at 75 you still have 2 eggs. Start again at 87.

continue 'splitting the difference' in this way until you get the answer.
Have I cracked it or will there be egg on my face?
Is this cheating?
http://www.theartofai...0inflatable%20egg.jpg

If it is then i'll go with what he ^^^^^^^^said. :)
factor, your approach to the problem is the right way to go, but you should not start on floor 50; if you start on floor 14 you would be able to tell in 14 drops or less.

(Start on 14; if it breaks try 1-13 order. If it does not break go to 27 and drop; if it breaks try 14-26 in order. if no break, go to 14+13+12 = 39,. etc etc).
The question was how many drops, factors answer could take 100 drops.

How about starting with every 10th floor and then you only have to check out the 9 floors below the one the first egg breaks on to get an answer giving a maximum of 19 drops.

Sure there is a way of getting it lower, but not that I can think of!
OK dr_b's way is lower :)
I think i can do it in less but i did get it a bit wrong. If it cracks from 50 rather than trying 1, 2,3 etc I should have split the difference to 25.
The trick is to keep splitting the difference.
I think you can do it in much fewer than 14 drops. I think 7.

I'll try it out later- not with eggs but on paper. I'll choose solutions such as floor 93, floor 67 and floor 37 and show how quickly you get each one. i think no more than 7 drops should do it
Problem there is factor what if it actually broke at 23 (for example)

drop one from floor 50 = egg breaks
drop two from floor 25 = egg breaks

Damm it no more eggs!
True. Is houldn't try to work these things out while cooking the tea. I'll think again. Maybe drb's solution is right.
Suppose the solution is k, that is, we can find the floor always within k drops. For our first drop, we could try a floor as high as floor k. This is because if the egg breaks, we can try all the floors below floor k and still determine the floor within k drops.

After dropping an egg on floor k and not broken, we now have k-1 remaining drops. Since our solution is k, we can now move up to floor k + (k-1). This still satisfies the total k drops criteria.

Then, if this doesn't work out, we can move up to floor k + (k-1) + (k-2), and so on so forth.

So, eventually we can move up as high as floor
k + (k-1) + (k-2) + (k-3) + ... + 1 = k(k+1)/2

The highest floor should be 99. Thus, we have:
k(k+1)/2 >= 99, from this, we get k=14

So, the answer is 14 maximum drops and we can find the floor.
I'm sure that's right, kawakiri . it does tell us the maximum number of drops.
So what floor should we drop our first egg from?
if the lift's not working I'm giving up after the 2nd floor
put them in the lift ?
Start on the 14th floor
Hmm, whats the story on using tiny mini bungee jump cords?
I agree with kawakiri.
Why not just eat the eggs for your tea and save running up & down the stairs
Hard boil 'em first?
wait until they hatch

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