Grades 11-12 Video Solutions 2012-2012_11-12

Video Transcription

A rectangular piece of paper ABCD measuring 4 cm by 16 cm is folded along the line MN so that vertex C coincides with vertex A, as shown in the picture.  What's the area of quadrilateral AN MD'?  So here it is a little bit bigger. We can notice that if we reflect across this middle line right here, we get exactly the same figure, so this is like a line of symmetry.  But that tells us that this little region right here and this region have the same area and together they make up the entire rectangle.  So the entire rectangle has area 64 cm², so the one we want has to be half of that, which is 32.

Video Summary

A rectangular piece of paper ABCD measuring 4 cm by 16 cm is folded along the line MN so that vertex C coincides with vertex A, as shown in the picture. What's the area of quadrilateral AN MD'? So here it is a little bit bigger. We can notice that if we reflect across this middle line right here, we get exactly the same figure, so this is like a line of symmetry. But that tells us that this little region right here and this region have the same area and together they make up the entire rectangle. So the entire rectangle has area 64 cm², so the one we want has to be half of that, which is 32.

Keywords

rectangle

folding

symmetry

area

geometry