Video Transcript
In the figure below, determine the
perimeter of the shaded part, given that the side length of every small square is a
unit.
In the picture or the figure that
we’re given, we can see a shaded shape, and it’s been drawn onto a square grid. And we’re told something about this
grid. We’re told the side length of every
small square is one unit. And so whatever measuring we need
to do in this question, we can do the measuring in units. Now we’re asked to determine or to
work out the perimeter of the shaded part. Now, what is a shape’s
perimeter? Perhaps you’ve heard people talking
about the perimeter fence around a field or the white lines that make up the
perimeter of a sports pitch.
If you’ve heard perimeter used like
this, then you’ll know that the word has got something to do with the outside of a
shape. Perimeter is the word we use to
describe the distance all around a shape. And so if we want to find the
perimeter of the shaded part that we can see here, we’re going to need to find the
distance all around it. Let’s start from this corner
here. Remember, we can’t stop until we
get back where we started. One, two, three, four, five, six,
seven, eight, nine, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20. And then the longest side, 21, 22,
23, 24, 25, 26, 27, 28. The distance all around this shape
is 28 square lengths. And because we’re told that the
side length of every small square is a unit, we can say that the perimeter of this
shaded part is 28 units.
