13 replies to this topic

[Sourabh]

There's a certain kind of egg about which you wonder: What is the highest floor of a 36-story building from which you can drop an egg without it breaking? All eggs of this kind are identical, so you can conduct experiments. Unfortunately, you only have 2 eggs. Fortunately, if an egg survives a drop without breaking, it is as good as new--that is, you can then conduct another dropping experiment with it. What is the smallest number of drops that is sure to determine the answer to your wonderings?

[plainglazed]

Am thinking

Spoiler for

you could always determine which floor with twelve drops? starting with the third floor and skipping every three floors

*** For anyone having spoiler issues, if you type between the tags [spoiler][/spoiler ]without quoted text in the leading tag it will work (also leave out the space)***

[DeeGee]

[spoiler]
8 drops.
Drop from 8th, 15th, 20th, 26th, 30th, 33rd, 35th and finally the 36th (to see if it even breaks at the 36th) floors
Whenever the first egg breaks, start dropping second egg from the next lower floor. The max number of drops will be 8
[/spoiler ]

Still having problems with the spoiler!

Edited by DeeGee, 21 July 2009 - 11:13 AM.

[Sourabh]

[spoiler]
8 drops.
Drop from 8th, 15th, 20th, 26th, 30th, 33rd, 35th and finally the 36th (to see if it even breaks at the 36th) floors
Whenever the first egg breaks, start dropping second egg from the next lower floor. The max number of drops will be 8
[/spoiler ]

Still having problems with the spoiler!

Its correct.......

its goes by formula

q(q+1)/2>=36

[RoteFreiherr]

Spoiler for

Its correct.......

its goes by formula

q(q+1)/2>=36

Hmm somehow I don't see this... if the egg breaks above the fifth floor, how can you determine that dropping the first from the 8th and the second from the 7th?

[riad135]

Have to agree with the last post - how would you know if it was floor 5 or 6?

Here's the real answer

Spoiler for

If you throw an egg out of the 36th floor with the pointy bit at the front and a slight spin, it will end up hitting the ground 'tip' first. The egg won't break as long as that happens - go try it!

[Dempsey Collins]

What is the smallest number of drops that is sure to determine the answer to your wonderings?

Spoiler for

Best Case Scenario: 2

Drop one from one height, it breaks. Drop the 2nd from the floor right below it, it survives. There's your answer.

[psychic_mind]

Spoiler for

Hmm somehow I don't see this... if the egg breaks above the fifth floor, how can you determine that dropping the first from the 8th and the second from the 7th?

If it breaks on the 8th floor you then try the 1st floor and the 2nd etc until you find where it breaks.

[RoteFreiherr]

If it breaks on the 8th floor you then try the 1st floor and the 2nd etc until you find where it breaks.

LOL my bad, yep it still makes 8 drops bad brain day

[Mesmer]

Drop your first egg from the following floors until (or if) it breaks:
6th, 12, 18, 24, 30, 35

Worst case comes if the egg breaks on either the 30th or 35th floor.

If it breaks on the 30th floor, then take the second egg and start at 26 and go through 28, for a total of 8. You can skip 25, since you know 24 worked. No need to go past 28 because you know 30 didn't work.

If it breaks on the 35th floor, then take the second egg and start at 32 and go to 33, for a total of 8.

All other breaks result in less than 8.

Good puzzle. Thanks.