Rope around the Earth
A string, ribbon or rope fits tightly round something round: a coin, a cake, a tree trunk, a pond, the Moon or the whole Earth. It is made a few centimetres longer and held out evenly. The student works out the gap all the way round, how much longer it must be for a given gap, or which of two gaps is bigger.
The statement gives the one fact needed: the distance round a circle is about 3 times the distance across. So 30 cm more round makes the loop 10 cm wider across, a 5 cm gap on each side, whatever the size of the thing inside. The working marks the two gaps across the middle of the loop.
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What changes each time
- A coin, a cake, a football, a tree, a table, a pond, the Moon or the Earth
- The gap, the extra length, or which gap is bigger
- Extra lengths that give a whole number of centimetres
More shapes and angles practice
- Sides and corners of 2D shapes (Grade 2)
- Faces, edges and vertices (Grade 3)
- Sorting quadrilaterals (Grade 3)
- Turning and flipping letters (Grade 3)
- Counting squares of every size (Grade 3)
- Inside or outside the loop (Grade 3)
- Which piece fills the gap? (Grade 3)
- Symmetry on a grid (Grade 4)
- Rotations and reflections (Grade 4)
- Reading a protractor (Grade 4)
- Parallel and perpendicular lines (Grade 4)
- Parts of a circle (Grade 4)
- Draw without lifting your pencil (Grade 4)
- Can these sticks make a triangle? (Grade 4)
- 3D shapes: side view (Grade 5)
- Rectangle in a quarter circle (Grade 5)
- Painted cube puzzle (Grade 5)
- Can dominoes cover the board? (Grade 5)
- Angles in a circle (Grade 6)
- Inscribed circle in a right triangle (Grade 8)