Let us check this out, let us go step no. 1 again that is to find the radius . now this
is our diameter, what is it? 65 so half of that is going to give us the radius there
to there from the center is going to be the R = ½ x d. going to half of diameter is half
of 65 that is going to be 32.5 that is going to be the radius . ok we have our radius there
– now, all we need to do now is write this up over here for easy to find ruminated ok
--- let us get the area that paces that orange paces semi-circular area across there and
now we know the area for a full circle is pi R squared and if you did not know that
now you know it so let us going to have, have we? So let us get the area for this orange
semi-circular paces -- there is our radius again –
and always remember the square root ½ x pi x 32.5 for squared that is going to give us
the answer of ½ x pi x 32.5 squared equals on your calculator all of that is going to
give us 1659.15cm. ok there is our front paces right over there and later on we got to double
it because we got the paces at the back so both those paces are the same so we got to
double that later so just remember this two semi-circle attach to the semi-circular cylinder.
Now let us go back to over step no. 2 is to find the guts underneath the floor the underneath
part here which is a rectangle let us work that out—so it is going to be length x breath
– that is 65 x31 on your calculator that is going to yield – 2015cm squared that
is our area for the rectangle underneath. Now what do we need to do next? Well we got
to go to the next step which is to find the area of this curve surface coming away across
there a half cylinder so that is going to be --
a ½ of and the area of the full cylinder the curve part all the way around 2 pi R H
and we are just going to half that out because obviously it is a half cylinder so let us
work that out it is going to be ½ x 2 pi R H so let me just bring this up over here
so ½ x 2 x pi x r h-- and the height which the height going across that way there that
is the height there that is 31. So let us put the numbers in there –
and rewrite this again 32.5— and us multiply by the height which is 31 there is the height
again 31. So let us multiply all the way across—just separate that ok ½ x 2 x pi x 32.5 x31 it
is really long one we are looking for that curve surface coming all the way around there.
That is going to give us an area of the curve surface all the way around there the half
curve surface all there is going to be 3165.15cm squared, ok that the area. Ok we need to add
everything up but before we add all the surfaces up we need to multiply the area for this orange
bit over here by two because there is another half of semi-circle around the other side
there. So remember we got 1659.15 we multiply that by 2 that is all we write it up twice
let us do that let us write up by twice it is going to make a lot easier. So let us add
them all together, so we are adding this one here x 2, so we write it down twice so it
is going to be – there is the two semi-circular areas then the base underneath that is going
to give us a grand total , here, here is the base if you remember? Yup—and then we have
the curved surface that is just up here. Ok that is going to give us a grand total, the
complete and entire surface area for all of this all 4 paces added together , there is
the 2 paces there, for the 2 semi-circle the front and the back, there we have the 25th
thing which is underneath and finally we have the curved part on the top 3165.15, put them
all in the calculator that is all going to add up to all together, in one her is – in
centimeter squared—8498.45cm squared.
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