lesson
Use dimensions, not a familiar-looking sketch
1 · Learn
Constructing a shape means following specified dimensions and angles accurately. Draw a measured base, position a protractor correctly and mark the requested angle before completing the shape. A rough sketch can plan the work but is not a precise construction.
A quadrilateral's interior angles total 360°. Splitting a pentagon from one vertex into three triangles shows a total of 540°. In a regular polygon all interior angles are equal; equal sides alone do not justify that assumption for every polygon.
2 · Worked example
A regular pentagon has total 3 × 180° = 540°, so each of its five equal angles is 108°. For an irregular pentagon, dividing by five only gives an average, not each actual angle.
3 · Your turn
A quadrilateral has angles 80°, 95° and 110°. Find the fourth. Why cannot you assume every quadrilateral angle is 90°?
Check your answer
The fourth is 360 - 285 = 75°. Only particular quadrilaterals, such as rectangles, have four right angles.
4 · Apply your learning
Construct an adult-specified triangle using a ruler and protractor, then measure and check its dimensions and angle sum.
Adult guidance and safety
Ask the learner to explain the method and check it using a different representation. Supply place-value grids, fraction strips, accurate diagrams and measuring tools where needed. These examples need varied practice; a short correct answer alone does not establish fluency.
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Check a calculation · Year 5 onward
Use this only when your teacher or adult allows a calculator for the task. Show your thinking first. It does not replace mental or written arithmetic and does not mark your lesson answer.
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