Mathematics and English progression

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Step 7 Objective

Deduce and use formulae for the area of a triangle, a parallelogram and a trapezium; calculate areas of compound shapes made from rectangles and triangles.

Examples of what pupils should know and be able to do

• Find rectangle length given triangle with same area - Rtf (rich text format) document (24Kb)

• Area of rectilinear shapes - Rtf (rich text format) document (48Kb)

• Area of triangles, rectangles and parallelograms - Rtf (rich text format) document (44Kb)

• FTMY789 p. 237 - Acrobat pdf document (44Kb)
  
• FTMY789 p. 235 - Acrobat pdf document (44Kb)

Probing questions

Why do you have to multiply the base by the perpendicular height to find the area of a parallelogram?

Right-angled triangles have half the area of the surrounding rectangle with the same base and height. What about non-right angled triangles?

The area of a triangle is 12 cm². What are the possible lengths of the base and height?

What other formulae for the area of two-dimensional shapes do you know?

Is there a formula for every two-dimensional shape?

What if pupils find this a barrier?

For areas of triangles start with right-angled triangles and establish that the area is half the area of the surrounding rectangle. Extend to any triangle; focus on pupils identifying a base and perpendicular height. Give more information in diagrams than needed. Discuss strategies to identify the necessary information.

Similarly for compound shapes.

• Y9 Booster lesson 9 - Microsoft word document (124Kb)
• T5 materials (add-on 6) - Microsoft word document (320Kb)