Teacher's Guide - Pearson

Extension Activity 12.2 (Student’s Book page 216)Perimeter of ABCD 5 50 cm Perimeter of A 1B 1C 1D 15 50 3 (​5__ ​) 5 125 cm2Area of ABCD 5 150 cm 2 and Area of A 1B 1C 1D 15 150 cm 2 .Ratio of perimeters is 5:2 and Ratio of area is 1:1.The two triangles are not similar because the ratio of area is not a square of the ratioof perimeters.Investigation (Student’s Book page 216)1. Side Perimeter Area1 cm 4 cm 1 cm 22 cm 8 cm 4 cm 23 cm 12 cm 9 cm 24 cm 16 cm 16 cm 25 cm 20 cm 25 cm 26 cm 24 cm 36 cm 2a) Perimeter doubles in each case.b) Area increases by a factor of 4.perimeterc) ________ ​ 5 4 ____ area​ 5 1, then 2, then 3, then 4, etc. So the perimeter increasessidesidelinearly and the area increases exponentially.d) Tapiwa is right. If you increase the sides by a constant factor, the areaincreases by more than that constant factor.2. Side Perimeter Area8 cm by 4 cm 24 324 cm by 2 cm 12 82 cm by 1 cm 6 23. When you increase the dimensions by scale factor k, the perimeter increases byscale factor k and area increases by scale factor k 2 .Activity 12.2 (Student’s Book page 218)1. 2; 42.1__5 ​; ___ ​ 125 ​3. 4; 44. 2; 468 EXPLORING MATHEMATICS FORM 3