Ex 11.2, 3 Find the missing values:
Base = 20 cm, Height = ?, Area = 246 cm2
Base = b
= 20 cm
Height = h
Area of parallelogram = b × h
246 = 20 × h
246/20 = h
123/10 = h
12.3 = h
h = 12.3 cm
∴ Height = 12.3 cm
(b) Base = ?, Height = 15 cm, Area = 154.5 cm2
Base = b
Height = h
= 15 cm
Area of parallelogram = b × h
154.5 = b × 15
154.5/15 = b
b = 154.5/15
b = 1545/15 × 1/10
b = 309/3 × 1/10
b = 103 × 1/10
b = 10.3 cm
∴ Base = 10.3 cm
(c) Base = ?, Height = 8.4 cm, Area = 48.72 cm2
Base = b
Height = h
= 8.4 cm
Area of parallelogram = b × h
48.72 = b × 8.4
48.72/8.4 = b
b = 48.72 × 1/8.4
b = 4872/100 × 10/84
b = 4872/10 × 1/84
b = 4872/84 × 1/10
b = 1281/21 × 1/10
b = 406/7 × 1/10
b = 58 × 1/10
b = 5.8 cm
∴ Base = 5.8 cm
(d) Base = 15.6 cm, Height = ?, Area = 16.38 cm2
Base = b
= 15.6 cm
Height = h
Area of parallelogram = b × h
16.38 = 15.6 h
16.38/15.6 = h
h = 16.38/15.6
h = 16.38 × 1/15.6
h = 1638/100 × 10/156
h = 1638/10 × 1/156
h = 1638/156 × 1/10
h = 819/78 × 1/10
h = 273/26 × 1/10
h = 21/2 × 1/10
h = 10.5 × 1/10
h = 1.05
∴ Height = 1.05 cm

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Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths and Science at Teachoo.