Video Transcript
A pendent is made out of
silver. Calculate the area of the face
of the pendant. And we have a diagram here
where the pendant is this shaded portion here.
So this pendant is a large
circle and then it has a smaller circle cut out to the middle of it. And it’s that sort of doughnut
shape that’s left that we’re looking to calculate the area of. So we can do this by working
out the area of the larger circle and then subtracting the area of the smaller
circle. Now the larger circle, if we
just think about it, has this radius here and that radius, well, it’s two
centimetres plus one centimetre. So this larger circle has a
radius of three centimetres. So our area formula is 𝜋𝑟
squared. And we’re gonna be doing the
large area subtract the small area. So we just need to substitute
in the relevant radii.
So for the larger circle, it’s
𝜋 multiplied by three squared and for the smaller circle it’s 𝜋 multiplied by
two squared. Now if we evaluate each of
these, we have nine 𝜋 subtract four 𝜋. And nine 𝜋 subtract four 𝜋 is
equal to five 𝜋. I haven’t been asked to leave
my answer in terms of 𝜋, so I’ll evaluate it as a decimal. And using my calculator, this
gives an answer of 15.7 centimetres squared to one decimal place. So that gives us the area of
this pendant here.
