N 4 Revision Area EF Area of a

N 4 Revision Area E&F

Area of a Rectangle 1 cm² = 1 square centimetre 6 cm 1 3 cm 2 3 4 5 6 6 square centimetres 3 rows of 6 squares = 3 x 6 = 18 square centimetres = 18 cm²

Area of a Rectangle: Short cut 6 cm (length) 3 cm (breadth) 6 x 3 = 18 cm² Area = length x breadth Must learn formula !

Area of a Rectangle Examples Find the area of : c) b) a) 10 m 6 cm 8 cm Area = l x b 14 m Area = l x b 7 mm 27 mm Area = l x b =8 x 6 = 14 x 10 = 27 x 7 = 48 cm² = 140 m² = 189 mm² Must show these 3 lines of working!

Exercise 1 180 cm 2 Find the area of the following shapes: 20 cm 9 cm 18 cm 36 cm 2 2 cm 60 cm 2 5 cm 12 cm 138 cm 2 200 m 2 10 m 25 m 4 cm 6 cm 147 cm 2 3 cm 49 cm 23 cm 25 m 2 2. 5 m 16 cm 2 8 m 81 m 2 9 m 9 m

Area of a Right-angled Triangle 4 cm Area of rectangle = l x b =7 x 4 = 28 cm² 7 cm Area of triangle= ½ x Area of rectangle = ½ x 28 = 14 cm²

Area of a Right-angled Triangle: Short cut 4 cm (height) 7 cm (base) Area of triangle = ½ x 7 x 4 = 14 cm² Area Δ = ½ x base x height Must learn formula !

Area of a Right-angled Triangle Examples Find the area of : 8 m b) a) 6 cm c) 32 m 20 cm Area = 60 cm² 10 mm 16 mm Area = 128 m² = 80 mm² Must show these 3 lines of working!

Exercise 2 Find the area of the following shapes: 8 cm 15 cm 45 cm 2 6 cm 10 cm 12 cm 60 cm 2 66 cm 2 6 cm 11 cm 44 cm 2 30 mm 225 mm 2 22 cm 4 cm 9 cm 2 4. 5 cm 15 mm 24 m 6 mm 27 mm 2 9 mm 127. 5 m 2 5 m 51 m 72 m 2 6 m

Area of Any Triangle Examples Find the area of : c) b) a) Area = 90 cm² 20 cm 62 cm 15 cm 18 cm 35 cm 18 cm 12 cm Be careful! Never use the sloping side in the calculation Area = 558 cm² = 350 mm² Must show these 3 lines of working!

Exercise 3 Find the area of the following shapes: 247 m 2 26 m 33 m 2 445. 5 m 27 m 30 cm 19 m 17 cm 2 15 cm 136 cm 16 cm 32 cm 25 cm 20 cm 300 cm 2 40 cm 6. 93 m 2 4. 2 m 2 16 cm 192 cm 20 cm 24 cm 3. 3 m 768 cm 2 4. 59 m 48 cm 2. 7 m 2 3. 4 m 21 cm 29 cm 420 cm 2 40 cm

Exercise 4 Find the area of the following shapes: 1012 m 246 m 44 m 6. 5 mm 42. 25 mm 2 6. 5 mm 156 cm 2 13 cm 12 cm 33 m 30. 66 m 28. 4 m 7. 3 m 8. 19 m 2 73 cm 2 55 cm 2640 cm 96 cm 54 cm 91. 8 cm 23. 4 cm 37 m 610. 5 m 2 4. 2 m 1736 cm 2 124 cm 3. 9 m 14 cm

? Area of Composite Shapes Example Find the area of : Area A = l x b = 24 x 7 24 cm 7 cm = 168 cm² A 6 cm B 39 cm 15 cm Area B = l x b = 15 x 6 = 90 cm² Total Area = 168 + 90 = 258 cm²

? Area of Composite Shapes Example Find the area of : Area A = l x b = 10 x 6 10 cm 6 cm = 60 cm² A B 13 cm Area B 3 cm = 9 cm² Total Area = 60 + 9 = 69 cm²

? Area of Composite Shapes Example Find the green shaded area A = l x b = 25 x 18 A 18 cm B = 450 cm² 7 cm Area B = l x b 7 cm 25 cm 3 cm =7 x 7 = 49 cm² Green shaded Area = 450 - 49 = 401 cm²

Exercise 5 Find the area of the following shapes: 11 cm 6 cm 86 cm 2 5 cm 8 cm 132 cm 2 4 cm 15 cm 3 cm Find the shaded area : 14 cm 2 10 cm 2120 cm 100 cm 2 6 cm 10 cm 8 cm 55 cm 40 cm

? Area of Composite Shapes Example Find the area of the trapezium : Area B = l x b Area A 8 cm =8 x 9 9 cm A 2 B 8 12 cm C 2 = 9 cm² Area A = 72 cm² =Area C = 9 cm² Total Area = 9 + 72 + 9 = 90 cm²

? Area of Composite Shapes Example 4 A 23 cm 15 B Find the area of the trapezium : 4 C = 15 x 18 = 36 cm² 18 cm Area A 15 cm Area B = l x b Area A = 270 cm² =Area C = 36 cm² Total Area = 36 + 270 + 36 = 90 cm²

Exercise 6 Find the area of the following trapeziums: 6 cm 14 cm 7 cm 119 cm 2 10 cm 85 cm 2 20 cm 45 cm 85 cm 2 189 cm 2 14 cm 37 cm 4. 5 cm 39 cm 1221 cm 2 38 cm 11 cm 20 cm 5 cm 28 cm 8. 5 cm 7. 4 cm 151. 7 cm 2 16. 5 cm