# Ex 11.2, 4 - Chapter 11 Class 7 Perimeter and Area

Last updated at Dec. 12, 2018 by Teachoo

Last updated at Dec. 12, 2018 by Teachoo

Transcript

Ex 11.2, 4 Find the missing values: (a) Base = 15 cm, Height = ?, Area = 87 cm2 Height = h = ? Base = b = 15 cm Given, Area of ∆ABC = 87 cm2 1/2 × b × h = 87 1/2 × 15 × h = 87 h = 87 × 2/15 h = 29 × 2/5 h = 58/5 h = 11.6 cm ∴ Height is 11.6 cm (a) Base = ?, Height = 31.4 mm, Area = 1256 mm2 Height = h = 31.4 mm Base = b = ? Given, Area of ∆ABC = 1256 mm2 1/2 × b × h = 1256 1/2 × b × 31.4 = 1256 b = 1256 × 2/31.4 b = 1256 × 2 × 1/31.4 b = 1256 × 2 × 10/(314 ) b = 1256 × 10/157 b = 1256/157 × 10 b = 8 × 10 b = 80 mm (a) Base = 22 cm, Height = ?, Area = 170.5 cm2 Height = h = ? Base = b = 22 cm Given, Area of ∆ABC = 170.5 cm2 1/2 × b × h = 170.5 1/2 × 22 × h = 170.5 11 × h = 170.5 h = 170.5/11 h = 1705/(11 × 10) h = 155/10 h = 15.5 cm ∴ Height is 15.5 cm

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