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Surface Area | Mathematics for GCSE/IGCSE - Year 11 PDF Download

What is surface area?

  • A face is a flat or curved surface that forms part of a three-dimensional shape.
  • The surface area of a three-dimensional shape is the total of the areas of all its faces.
  • Observe how we extend a two-dimensional concept (area) into three dimensions in this context.

How do I find the surface area of cuboids, pyramids, and prisms?

  • In cuboids, polygonal-based pyramids, and polygonal-based prisms (i.e., pyramids and prisms with straight-sided bases), all faces are flat.
  • To find the surface area, simply sum the areas of these flat faces.
  • Drawing a 2D net of the 3D shape can be very useful when calculating surface area.
  • Example:
    • The base of a square-based pyramid has sides measuring 15 cm.
    • The triangular faces are identical isosceles triangles, each with a height of 23 cm from the base to the top of the pyramid.
    • Calculate the total surface area of the pyramid.
    • Draw a net for the shape.

Surface Area | Mathematics for GCSE/IGCSE - Year 11

  • Area of square base =152 = 225 cm2
  • Area of one triangular face = ½ base × height = ½ × 15 × 23 =172.5 cm2
  • Total surface area =225 + 4 × 172.5 = 915 cm2

How to find the surface area of cylinders, cones, and spheres?

  • All three shapes - cylinders, cones, and spheres - have curved faces, requiring careful consideration when calculating their surface areas.

1. The net of a cylinder consists of two circles and a rectangle 

Surface Area | Mathematics for GCSE/IGCSE - Year 11

  • The curved surface area of a cylinder is bold 2 πrh
  • The total surface area of a cylinder with base radius r and height h is therefore given by: Total surface area of a cylinder = 2 πr+ 2 πrh

2. The net of a cone consists of the circular base along with the curved surface area

Surface Area | Mathematics for GCSE/IGCSE - Year 11

  • The slant height in a cone diagram is the oblique height, whereas h represents the vertical height of the cone.
  • To calculate the surface area of a cone with base radius r and slant height l, utilize the following formulas:
    • Curved surface area of a cone = πrl
    • Total surface area of a cone = πr2 + πrl

3. To find the surface area of a sphere with radius r, use the formula

  • Surface area of a sphere = 4πr2

Surface Area | Mathematics for GCSE/IGCSE - Year 11

  • Be careful when calculating the surface area of a hemisphere:

Surface Area | Mathematics for GCSE/IGCSE - Year 11

  • When computing the surface area of a hemisphere, account for the curved part (half of a sphere) and the flat circular face. The total surface area is 3πr2.
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FAQs on Surface Area - Mathematics for GCSE/IGCSE - Year 11

1. What is the formula for calculating the surface area of a cuboid?
Ans. The formula for the surface area of a cuboid is 2lw + 2lh + 2wh, where l, w, and h are the length, width, and height of the cuboid, respectively.
2. How do you find the surface area of a pyramid?
Ans. To find the surface area of a pyramid, you can use the formula A = 0.5 × perimeter of base × slant height + base area, where the base area can be calculated separately depending on the shape of the base.
3. What is the surface area of a prism and how is it calculated?
Ans. The surface area of a prism is the sum of the areas of all its faces. It can be calculated by finding the area of each face and then adding them together.
4. Are there any shortcuts or tricks to calculating surface area quickly?
Ans. One shortcut for calculating the surface area of a cuboid is to add the areas of the faces in pairs (l x w, l x h, w x h) and then double the result. This can help simplify the calculation process.
5. How can I use the surface area formulas in real-life scenarios?
Ans. Understanding surface area formulas can be useful in various real-life situations, such as calculating the amount of paint needed to cover a surface, determining the material needed to construct a packaging box, or estimating the cost of materials for a construction project.
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