Area and volume in similar figures
3 exam-style questions. Answers and the mark for each step are on the last page.
- Question 1
Two cylinders are mathematically similar. The smaller has height 6 cm and volume . The larger has height 9 cm.
(a) Work out the volume of the larger cylinder.
- Question 2
Two solid shapes are mathematically similar. Their surface areas are and . The smaller shape has volume .
(a) Work out the volume of the larger shape.
- Question 3
A solid cone is cut by a plane parallel to its base, one third of the way down from the vertex (measured along the height). This cuts off a small cone and leaves a frustum.
(a) Show that the ratio of the volume of the small cone to the volume of the frustum is .
Answers and marks
Question 1
(a)
- P1 Length scale factor 1.5.
- P1 Cubing it for volume.
- A1 .
Question 2
(a)
- P1 Area factor .
- P1 Square-rooting to the length factor .
- P1 Cubing to the volume factor .
- A1 .
Question 3
(a) Small cone ; frustum .
- P1 Length scale factor for the small cone.
- P1 Volume factor .
- P1 The frustum as .
- A1 Reaching with the frustum expressed correctly.