
Elementary Math Fractions, Percentages, Word Problems, Equations, Inequations, Factorization, Expansion 
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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:
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 
Senior Member Joined: Nov 2010 From: Indonesia Posts: 1,519 Thanks: 120 Math Focus: Trigonometry and Logarithm  Except that the other two may get fallen due to the vibration impact.

July 4th, 2014, 02:25 AM  #9  
Senior Member Joined: Apr 2014 From: Glasgow Posts: 2,080 Thanks: 698 Math Focus: Physics, mathematical modelling, numerical and computational solutions  Quote:
$\displaystyle 0 \leq x \leq 3, x \in \mathbb{N}^0$, 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 nonzero at the time of the rock being thrown.  
July 14th, 2014, 02:55 AM  #10 
Member Joined: Jun 2014 From: Brighton Posts: 49 Thanks: 2  

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