Practise the method.Example 1A right triangular prism has cross-section base 12cm, perpendicular height 5cm and prism length 6cm. Find its volume, in cm3.Right triangular prismRight triangular prismPrism with a right triangular cross-section: perpendicular base 12 cm, height 5 cm; prism length 6 cm. Diagram not to scale. Use the labelled measurements.12 cm5 cm6 cmDiagram not to scaleShow worked answerAnswer: 180Cross-section area = ½ ×12×5=30cm2.Multiply by the prism length: 30×6=180cm3.Example 2A cylinder has radius 6cm and height 5cm. Find its volume, in cm3. Use π=3. Give an exact answer.CylinderCylinderCylinder with radius 6 cm and perpendicular height 5 cm. Diagram not to scale. Use the labelled measurements.6 cm5 cmDiagram not to scaleShow worked answerAnswer: 540Volume =πr2h.Using π=3:3×62×5=540cm3.Example 3A right triangular prism has volume 120cm3. Its cross-section has perpendicular base 10cm and height 4cm. Find the prism length x, in cm.Right triangular prismRight triangular prismPrism with a right triangular cross-section: perpendicular base 10 cm, height 4 cm; prism length x cm. Diagram not to scale. Use the labelled measurements.10 cm4 cmx cmDiagram not to scaleShow worked answerAnswer: 6Cross-section area = ½ ×10×4=20cm2.Length =20120=6cm.