GCSE Mathematics (9-1)

19.6 Composite shapes and solids — Practise with help

Warm-up: remember

  1. Find the volume of a cuboid 3×4×53\times4\times5 cm. 2. Find the area of a 99 cm by 66 cm rectangle.
Check your answers
  1. 60 cm360\text{ cm}^3. 2. 54 cm254\text{ cm}^2.

Practise with help

Attempt each question first. Open the hint, then the next step, when needed.

1. A shape is made from a 5 cm by 4 cm rectangle and a 5 cm by 3 cm rectangle joined along a 5 cm side without overlap. Work out its total area.

Hint

Split the shape into its two rectangles and add their areas.

Next step

Find 5×4+5×35\times4+5\times3.

Full working

5×4+5×3=20+15=35 cm25\times4+5\times3=20+15=35\text{ cm}^2.

2. A solid is made from a cuboid 6 cm by 4 cm by 3 cm and a cuboid 2 cm by 4 cm by 3 cm joined without overlap. Work out its total volume.

Hint

Find each cuboid's volume, then add them.

Next step

Find 6×4×3+2×4×36\times4\times3+2\times4\times3.

Full working

6×4×3+2×4×3=72+24=96 cm36\times4\times3+2\times4\times3=72+24=96\text{ cm}^3.

3. A semicircle of radius 3 cm is joined to a rectangle 6 cm by 4 cm along the 6 cm side. Work out the outside perimeter in terms of π.

Hint

The outside is the arc plus the three straight sides that are not joined.

Next step

Find the arc as half the circumference: 12×2π×3=3π\frac12\times2\pi\times3=3\pi.

Full working

The straight part is 6+4+4=146+4+4=14. The outside perimeter is 14+3π cm14+3\pi\text{ cm}.

Try the remaining questions without opening the full working.

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