Teacher's Guide - Pearson

Exercise 12.2 (Student’s Book page 214)1. a) 6:5 and 36:25b) 4:9 and 4:92. a) 1__2 ​bh ∴ h 5 ____ ​ Area1__​ 5 ___ ​ 60​ 5 12 cm2 ​b 5b) h 5 ​2__3 ​ 3 ___ ​ 121 ​ 5 8 cm; b 5 ​ 2__3 ​ 3 ___ ​ 101 ​ 5 ___ ​ 203 ​ = 6​ 2__3 cmArea DEF 5 ​4__9 ​ 3 ___ ​ 601 ​ 5 ____ ​ 2409 ​ 5 26​ 6__9 5 26​ 2__3 cm2c) Area 5 ​1__ ​bh = ​1__2 2 ​ 3 ___ ​ 203 ​ 3 ​ 8__1 ​ 5 ____ ​ 1606 ​ 5 26​ 4__6 ​3. a)9__4 ​b)9__4 ​ 3 ____ ​ 1001 ​ 5 225%c) Area 1: 1__ ​ 3 60 3 40 5 1 200 cm22New dimensions: 3__2 ​ 3 60 5 90 cm 3__ ​ 3 40 5 60 cm2Area 2: 1__ ​ 3 90 3 60 5 2 700 cm22This is the same as 2.25 3 1200.BC4. a) ___FH ​ 5 ___ ​ DAGE ​b) Ratio ABCD:EFHG5 ​6__4 ​ 5 3:2c)x__8 ​ 5 ​ 2__3 ​ ∴ x 5 ___ ​ 16​ cm 5 5.3 cm3y__5 ​ 5 ​ 3__2 ​ ∴ y 5 ___ ​ 15​ 5 7.5 cm2d) Perimeter ABCD:Perimeter EFHG 5 3:2Area ABCD:Area EFHG 5 9:4e) Area EFHG 5 ​4__9 ​ 3 ___ ​ 81​ 5 36 cm215. a) One window:Frame perimeter 5 2(2 1 1.5) 5 7 mLength of slats 5 (4 3 1.5) 1 (2 3 2) 5 10 mCost per window:Frame 5 7 3 20.50 5 P143.50Slats 5 10 3 15.25 5 P152.50Total 5 P296/windowCost of 9 windows: P2 664b) 4:25c) Cost 5 ​2__ ​ 3 296 5 P118.405Chapter 12: Area and perimeter67