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Subjects · Leaving Cert Design & Communication Graphics (DCG)

Leaving Cert Design & Communication Graphics (DCG): Surface development & envelopment

How often Surface development & envelopment comes up on the Design & Communication Graphics papers, every year it was asked, and questions to try.

HL Asked on 6 of the last 9 Higher Level papers, most recently in 2024. most years

Surface development & envelopment, Higher Level(8 marks)

Quick ones on Surface development & envelopment.

(a)A cylinder of 40 mm diameter is developed. How long is the rectangle?
  1. ≈62.8 mm
  2. ≈125.7 mm
  3. ≈251.3 mm
(b)Developing a cut cone: how do you find a point's true distance from the apex along its generator?
  1. Measure its plan distance from the centre
  2. Measure it along the axis
  3. Project it across to an outside generator
(c)A right cone has base radius 30 mm and slant height 90 mm. What is the angle of its development sector?
  1. 120°
  2. 108°
  3. 60°
Show the answers

(a) ≈125.7 mm

(b) Project it across to an outside generator

(c) 120°

Your turn: Higher Level questions on Surface development & envelopment.

Higher Level

Asked on 6 of the last 9 Higher Level papers, most recently in 2024. most years

Every paper, year by year

YearWhere it came up
2025Not asked
2024B2
2023A1
2022A4
2021Not asked
2019Not asked
2018B2
2017B3
2016A1

Links open the State Examinations Commission’s paper for that year.

More Surface development & envelopment questions

Surface development & envelopment, 2 marks

How is the surface of a sphere approximately developed?

  1. As one exact circle of equal area
  2. As a single rectangle, like a cylinder
  3. As gores (orange-peel segments)
Show the answer

As gores (orange-peel segments)

A sphere is doubly curved and cannot be developed exactly. It is split into gores (or zones), each treated as part of a cylinder or cone, to give an approximate development.

Surface development & envelopment, 2 marks

Where is the seam of a sheet-metal development usually placed?

  1. Across the middle of the piece
  2. Along the shortest line or edge
  3. Along the longest line or edge
Show the answer

Along the shortest line or edge

Putting the joint on the shortest line keeps the seam, and the welding, riveting or gluing it needs, as short as possible.

Surface development & envelopment, 2 marks

Which method is used to develop a right cone or pyramid?

  1. Radial-line development
  2. Parallel-line development
  3. The auxiliary circle method
Show the answer

Radial-line development

All the generators or edges radiate from the apex, so the development is set out from one centre with true-length radii. Prisms and cylinders use parallel-line development.

Other Design & Communication Graphics (DCG) topics

All of Leaving Cert Design & Communication Graphics (DCG)