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Circle of Children

Math brain teasers require computations to solve.

 

Fun:*** (2.81)
Difficulty:** (1.27)
Category:Math
Submitted By:sk8ergrl

 



A number of children are standing in a circle. They are evenly spaced and the 7th child is directly opposite the 18th child. How many children are there altogether?


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Answer

22; in half of the circle there are 11 children because 18-7=11. Multiply 11x2=22!
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Comments

Posted by onlyeeyore on Jun 15, 2005

As usual I got this math teaser the long way. I've got to bone up on my algebra!

Posted by Riddlerman on Jun 15, 2005

Algebra ain't anything to do with it. Just figure 10 kids either side of them (10) Double it as there are two sides (20), then add the two kids themselves (22)

Bit EZ but i enjoyed it. Thanks.

Posted by sk8ergrl on Jun 15, 2005

riddle is right. There is nothing to do with Algebra. I'm glad everyone seems to like it

Posted by BrUnEttEcUtiE on Jun 15, 2005

We do these as bonus questions in school all the time!

Posted by sweetime on Jun 15, 2005

my brain hurts
i got 20 but i'm not entirely sure how

Posted by tamjp on Jun 16, 2005

I needed the hint.
but ast least then I got it!

good one!

Posted by PCDguitar on Jun 17, 2005

good 1 even tho i dont understand y u need to subtract 7 from 18 to get 11 to multiplay it by two?

Posted by Question_Mark on Jun 17, 2005

Simple, but good.

Posted by froggygg on Jun 22, 2005

Good teaser!

Posted by amanduh05 on Jun 23, 2005

good 1

Posted by sk8ergrl on Mar 20, 2006

Thanx!!!

Posted by tintiniscool on Aug 06, 2006

Fun!

Posted by opqpop on Sep 11, 2010

I'm such an idiot. I figured out there were 10 kids on the right, and then figured out there were 6 kids before the 7th kid on the left, and hence 4 kids after the 18th kid to the left, for a total of 18 + 4 = 22 kids.

Then I realized I could have just doubled 10 and added 2.

Sigh I'm ashamed of my stupidity.

Posted by doctapeppaman on Sep 27, 2012

The solution assumes that the children are arranged consecutively around the circle.

Posted by Jimbo on Jun 03, 2013

The question may be considered by solving a simpler problem. If 4 kids stand in a circle, 1 is opposite 3 and 2 is opposite 4. The difference in position is always 2. Double it to find the number.
So 18 - 7 = 11. 2 * 11 = 22.

Posted by Jimbo on Jun 03, 2013

Good teaser BTW.

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