maths
posted by nabiha .
a cylindrical cake with radius 12cm and height 10cm has a slice cut out. The shape of the top of the slice is a sector of the circle that forms the top of the cake. Exluding the sliced piece, the angle is 320 degrees.
a) Calculate the area on top of the slice that has been cut out.
b) Calculate the volume of the cake that remains after the slice has been removed.
c) Calculate the surface area of the cake that remains after the slice has been removed.
i particularly need to know how to do c) This is because I have already worked out the answers to a) and b)
c)
I worked out the area of the cake using the sector 320 degrees, but there is also a bottom so you therefore have to multiple it by 2.
same with when you cut the slice there are 2 rectangular sides. obviously round the circumference of the cake there is a long rectangular shape but because it is a cake it looks curved. because you want the whole surface area once you've sliced it you have to add all the figures. Here are my workings:
10*12=120*2=240cm squared
area of base=320 over 360*pie*12 squared=402.1238597*2 cos theres a top and bottom 4 a cake= 804.2477193
w=320 over 360*2*pie*12 ( multiply this by height of 10cm= 670.2064328
add these: 240+804.2477193+670.2064328=1714.454852 so surface area = 1414cm squared
however in the book the answer was 1474cm squared. i figured out they didn't add the 240 on which are the bits on the side which is right?

maths 
Reiny
It's me again.
I now fully understand what you are asking for in your part c)
I agree with your calculations of the exposed area of the top and bottom of the remaining cake
area (top+bottom) = 2(320/360)(144π) = 804.25 (you had that)
area (exposed outer side) = (320/360)(2π(12))(10) = 670.21 (you had that also)
if we add just those two sums we get 1474.45 which is their answer.
So it does look like they forgot the 2 rectangular areas of the inside of the remaining cake, which you calculated correctly as well, which were 2(12)(10) = 240
so the correct answer should have been the sum of those 3 answers or 1714.45 which you also had.
I again apologize for my error in our last exchange. 
maths 
Sasha Kapadia
that is totally wrong
Respond to this Question
Similar Questions

maths
a cylindrical cake with radius 12cm and height 10cm has a slice cut out. The shape of the top of the slice is a sector of the circle that forms the top of the cake. a) Calculate the area on top of the slice that has been cut out. b) … 
maths
a cylindrical cake with radius 12cm and height 10cm has a slice cut out. The shape of the top of the slice is a sector of the circle that forms the top of the cake. a) Calculate the area on top of the slice that has been cut out. b) … 
maths
a cylindrical cake with radius 12cm and height 10cm has a slice cut out. The shape of the top of the slice is a sector of the circle that forms the top of the cake. a) Calculate the area on top of the slice that has been cut out. b) … 
maths
a cylindrical cake with radius 12cm and height 10cm has a slice cut out. The shape of the top of the slice is a sector of the circle that forms the top of the cake. Exluding the sliced piece, the angle is 320 degrees. a) Calculate … 
maths
a cylindrical cake with radius 12cm and height 10cm has a slice cut out. The shape of the top of the slice is a sector of the circle that forms the top of the cake. Exluding the sliced piece, the angle is 320 degrees. a) Calculate … 
maths
a cylindrical cake with radius 12cm and height 10cm has a slice cut out. The shape of the top of the slice is a sector of the circle that forms the top of the cake. Exluding the sliced piece, the angle is 320 degrees. a) Calculate … 
maths
a cylindrical cake with radius 12cm and height 10cm has a slice cut out. The shape of the top of the slice is a sector of the circle that forms the top of the cake. Exluding the sliced piece, the angle is 320 degrees. a) Calculate … 
math
Janet bakes a cake in the shape of a cube with side length x (in inches). She makes a vertical cut parallel to one of the sides, resulting in a slice with width y where x is 5 times as large as y. a) Define a function h that determines … 
algebra
Deb is slicing up a cake for three people. The cake is 45cm long and the second piece is 10cm longer than the first, and the third piece is 5 cm less than double the first . How big is each slice? 
Maths
A cylindrical birthday cake of radius 23cm and height 12cm is to be shared equally among 18 people at a party,the piece of cake was shaped as AOB to give 20 degrees,hence prove that.Also calculate the area of cylindrical cake.