A symmetry question
Moderators: Section Moderators, Forum Moderators
-
- Posts: 10
- Joined: Sat May 28, 2011 3:26 pm
A symmetry question
Dear All
Could anyone out help in resolving a question that my niece and I are having a disagreement with ?
The question is :
A square grid is separated into 16 small squares ( a diagram of a 4 by 4 square is given but I can't seem to insert diagrams here - each corner is identified as A B C and D and diagonal line from AC )
How many ways can two squares be shaded so that the grid has symmetry about the diagonal AC if :
a) the two squares must not include the diagonal line ?
b) the two squares must include the diagonal line ?
c) On the grids below ( again six 4 by 4 squares are given with A B C D as the corners with two diagonal lines AC and BD),
show all the ways exactly two squares can be shaded so that the grid has symmetry about the two diagonal lines AC and BD. The question also says - (You may not need to use all the grids).
If hermanmunster or anyone else out there can help - then we would be very grateful and would like to thank you in advance
Could anyone out help in resolving a question that my niece and I are having a disagreement with ?
The question is :
A square grid is separated into 16 small squares ( a diagram of a 4 by 4 square is given but I can't seem to insert diagrams here - each corner is identified as A B C and D and diagonal line from AC )
How many ways can two squares be shaded so that the grid has symmetry about the diagonal AC if :
a) the two squares must not include the diagonal line ?
b) the two squares must include the diagonal line ?
c) On the grids below ( again six 4 by 4 squares are given with A B C D as the corners with two diagonal lines AC and BD),
show all the ways exactly two squares can be shaded so that the grid has symmetry about the two diagonal lines AC and BD. The question also says - (You may not need to use all the grids).
If hermanmunster or anyone else out there can help - then we would be very grateful and would like to thank you in advance
Re: RE : A symmetry question
teacher_mum wrote:A square grid is separated into 16 small squares ( a diagram of a 4 by 4 square is given but I can't seem to insert diagrams here - each corner is identified as A B C and D and diagonal line from AC )
How many ways can two squares be shaded so that the grid has symmetry about the diagonal AC if :
a) the two squares must not include the diagonal line ?
b) the two squares must include the diagonal line ?
Code: Select all
A _____________ B
|__|__|__|__|
|__|__|__|__|
|__|__|__|__|
|__|__|__|__|
D C
b) If one of the squares is on the diagonal, the other must be as well to obtain symmetry, so the question becomes how many ways can we choose 2 squares out of the 4 on the diagonal. Well, there are 4 ways to choose the first square, times 3 to choose the second (once one square is taken), divided by 2 because we've considered each combination twice, so again 6 possible answers.
-
- Posts: 10
- Joined: Sat May 28, 2011 3:26 pm
Re: A symmetry question
Dear WP
Thank you very much for your help
I had 6 for part (i) but 4 for (ii) but you are right it should 6 as well.
Thanks once again
Thank you very much for your help
I had 6 for part (i) but 4 for (ii) but you are right it should 6 as well.
Thanks once again
Re: A symmetry question
Hi There
For part c) for symmetry around 2 axes, my answer was 4 possibilities - could someone please confirm if this is correct?
Thanks
For part c) for symmetry around 2 axes, my answer was 4 possibilities - could someone please confirm if this is correct?
Thanks