The Outwood Grange Family of Schools Perimeters (teacher notes): 1.The word perimeter is often used to denote the boundary of a 2D figure. In maths it means the length of the outer edge. 2.The shapes in this section are either triangles, or are made from rectangles. So if an angle looks like a right angle, you can assume that it is a right angle. 3.On the Easier section, for the 1 st two, just add all of the numbers together. On the 3 rd one, we need to realise the missing top side and left side are the same sizes as the 2 given sides (it’s a rectangle). 4.On the Medium section, we need to remember that 1000mm=100cm=1m (or 10mm=1cm & 100cm=1m) 5.On the Hard section, for (a) we need to know that an isosceles triangle has 2 equal length sides. We then do either =24.4 and then ½ x 24.4=12.2 or, x10.9= =13.5 (depending on which 2 sides are equal). For (b) imagine walking around the shape. In shape C, we would have to walk a small extra distance around the highlighted part here: 4cm Please note alternative challenge on slide 4

The Outwood Grange Family of Schools Perimeters: Harder a.An isosceles triangle has perimeter 35.3cm and base length 10.9cm. How long are the other 2 sides? b.Which shape has a different perimeter to the rest? Easier a.What are the perimeters of these 3 shapes? 4cm 5cm 8cm 5cm 6cm 8cm Medium a.A triangle has sides of length 2.3cm, 31mm & 0.018m. Find its perimeter in (i) mm (ii) cm (iii) m. 4cm A E D C B

The Outwood Grange Family of Schools Perimeters: Harder a.An isosceles triangle has perimeter 35.3cm and base length 10.9cm. How long are the other 2 sides? b.Which shape has a different perimeter to the rest? Easier a.What are the perimeters of these 3 shapes? 4cm 5cm 8cm 5cm 6cm 8cm Medium a.A triangle has sides of length 2.3cm, 31mm & 0.018m. Find its perimeter in (i) mm (ii) cm (iii) m. 4cm A E D C B 18cm 28c m 72mm7.2cm 0.072m 12.2cm or 13.5cm

The Outwood Grange Family of Schools Perimeter Can you find the largest perimeter of a rectangle with an area of 20cm ² If you have 20m of fencing what shape gives you the biggest area? (start with rectangles!) C