Determining Cube Nets from given Nets Video Lecture | Mathematics (Maths) Class 7 (Old NCERT)

in the previous session we saw how we
can convert a net to its solid this
session will be a bit different we will
be given a few nets and asked to find
out if cubes can be formed out of them
here's the first net the second one the
third one and the fourth one we assume
that each face in each of the nets is a
square these are the four nets we have
how many of them when folded would
result in a cube let's look at the first
figure we had seen in the previous
session that the best way to figure out
the solid from its net would be by
placing it on a plane how can we do that
here let's draw these four squares on a
plane surface first they would look a
bit like this and these two square faces
are attached to the middle two square
faces if they are made vertical they
will be drawn like this these two square
faces you see are these two in the
original figure they have been made
vertical that's all now take a moment
and think if we can form a cube out of
this shape
let's try we can make these two square
faces vertical to get a better idea this
is how the figure will look when they
are made perpendicular to the plane
surface now it's pretty evident that app
you cannot be formed out of this no
matter how you fold it it means that a
cube cannot be formed with this net we
move on to the second net now pause the
video and think if a cube can be formed
with it we use the same technique to
start off we draw the net as if it's
lying on a plane these four faces can be
drawn like this and the two faces
attached to these two squares can be
drawn like this
this net on a plane surface would look
like this can a cube be formed out of
this to get a better idea we can make
these two square faces vertical and that
will give us this figure now we still
can't say if a cube can be formed out of
this how do we fold it further it's easy
it just requires a little bit of
imagination if Beetles the two square
faces on the left onto this one and make
the square at the extreme right vertical
we get this figure four vertical faces
and two horizontal understand this well
the two square faces on the Left were
tilted on to this one and the square
face at the extreme right was rotated to
make it vertical can we make a cube out
of this figure of course we can if we
tilt these three to the left we get a
perfect close cube like this one yes a
cube can be formed out of this net what
about the third net can a cube be formed
out of it pause the video and give it a
thought
it shouldn't have taken you much time if
you observe the figure well it has just
five faces not enough to form a cube
because a cube has six faces so a cube
cannot be formed from this net and what
about the fourth figure pause the video
and try it out
this is how the net will look if placed
on a plain surface for faces in the same
line and two more attach to one of the
squares making these two square faces
vertical will give us a figure which
looks like this two vertical faces and
four horizontal ones what do you think
of it now can a cube be formed
imagine that we tilt these two towards
the two vertical squares and this one
clockwise what will we get we will get a
figure like this these two were rotated
anti-clockwise and this square face was
made vertical by rotating it clockwise
now if we just drop the square face
towards the left we will get a cube so
yes a cube can be formed out of the
forth net all this we did in between is
what you supposed to imagine in your
head and it's not too difficult a good
way to excel at this is by understanding
the concepts well and then lots of
practice
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