Birthday Cake
Math brain teasers require computations to solve.
Suppose you are given a birthday cake which is round in shape (like a perfect circle) and you are asked to make eight equal pieces out of it by using a knife only three times. How would you proceed?
Answer
Use the knife a first time to cut it across one of its diameters. Then use the knife a second time to cut across another diameter and you will have four equal parts. Use the knife a third time to cut the cake horizontally, half way across its thickness, and you have the eight equal pieces!!!
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Comments
Sawb
Jul 04, 2001
 Although they are the same size, they aren`t really equal because 4 are from the top and 4 are from the bottom. You could cut the cake twice as the answer states, but then move the pieces so they are all in a line and make one final long cut splitting all 4 pieces into 8 completely equal pieces. eh? 
Mogmatt16
May 07, 2002
 You know, I exhaust most teaser books i know of, go searching for new ones, and run into ones i've already seen. 
Rowsdower
Jan 11, 2004
 Half of the little kids would be ticked to not get any icing as well! And if you saw this one before, Mogmatt, you could have submitted it first and not have had to complain. 
canu
Jul 14, 2004
 For the 3rd cut, you could also put the quarter pieces on top of each other and cut straight down. 
dishu
May 26, 2006
 this shud b in trick not maths 
dishu
May 26, 2006
 this shud b in trick not maths 
JessicaLynn
Jun 16, 2006
 I agree with canu. Then all the little kids would get icving too. 
kayleeskitties
Aug 05, 2006
 I don't think a piece of cake is worth that. Who would limit you to only 3 cuts? 
Sweetooth49
Aug 16, 2007
 Cute, but then the peices are smaller. I call a bottom piece! 
chickwithbrains
Sep 27, 2007
 I don't understand the way that the answer is worded at all  did they mean that after the first two cuts are made the pieces are stacked on top of each other or in a line and **then** the final cut is made? Because otherwise, if the four pieces are left as they are, it is impossible to just make one more cut and end up with eight equal pieces.
??? 
javaguru
Jan 29, 2009
 My solution was to cut an inner circle with a radius of 1/sqrt(2) times the cake radius and then cut two diagonals. At least everyone gets some of the top icing that way. 
Jimbo
Mar 28, 2009
 To heck with the problems, I just Love Java's solutions  Way to go! 
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