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 June 26th, 2014, 05:57 PM #1 Banned Camp   Joined: Feb 2013 Posts: 224 Thanks: 6 Very old riddle There are 3 birds sitting on a branch of a tree. If you throw a rock and knock 1 bird down, how many birds are left on the tree?
 June 26th, 2014, 08:44 PM #2 Math Team   Joined: Dec 2013 From: Colombia Posts: 7,090 Thanks: 2360 Math Focus: Mainly analysis and algebra None
 June 26th, 2014, 09:12 PM #3 Math Team   Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 11,057 Thanks: 721 2, since a rock makes no noise to scare away...you need a gunshot
 June 26th, 2014, 09:18 PM #4 Banned Camp   Joined: Feb 2013 Posts: 224 Thanks: 6 The answer is none. The beauty of the riddle is that you can't just simply plug in numbers in real life. Real life has a lot of variables. If it were 3 apples on a tree, then 2 would be left on the branch.
 June 26th, 2014, 11:03 PM #5 Math Team   Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 11,057 Thanks: 721 Here's another: 3 lights in a room; the 3 switches are outside the room. How can you determine which light each switch is connected to? You cannot see inside the room while you're doing this; plus you can enter the room only once.
 June 26th, 2014, 11:07 PM #6 Math Team   Joined: Dec 2013 From: Colombia Posts: 7,090 Thanks: 2360 Math Focus: Mainly analysis and algebra If you know that they are all off to start with, you:flip one switch; wait a few minutes; flip the switch again; flip another switch; enter. It's a bit harder if they aren't all off to start with.
 June 26th, 2014, 11:15 PM #7 Math Team   Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 11,057 Thanks: 721 Correct Archie...you get the Electrician Job
July 3rd, 2014, 09:00 PM   #8
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Quote:
 Originally Posted by long_quach The answer is none. The beauty of the riddle is that you can't just simply plug in numbers in real life. Real life has a lot of variables. If it were 3 apples on a tree, then 2 would be left on the branch.
Except that the other two may get fallen due to the vibration impact.

July 4th, 2014, 02:25 AM   #9
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Quote:
 Originally Posted by long_quach There are 3 birds sitting on a branch of a tree. If you throw a rock and knock 1 bird down, how many birds are left on the tree?
Assuming an isolated, closed system,

$\displaystyle 0 \leq x \leq 3, x \in \mathbb{N}^0$,

where $\displaystyle x$ is the number of birds sitting on the branch in the tree and the function describing the rate of change of number of birds in the tree as a function of time is unknown, but non-zero at the time of the rock being thrown.

July 14th, 2014, 02:55 AM   #10
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Quote:
 Originally Posted by long_quach There are 3 birds sitting on a branch of a tree. If you throw a rock and knock 1 bird down, how many birds are left on the tree?
None

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