Ex 11.4, 3 - A picture is painted on a cardboard 8 cm long and 5 wide

Ex 11.4, 3 - Chapter 11 Class 7 Perimeter and Area - Part 2
Ex 11.4, 3 - Chapter 11 Class 7 Perimeter and Area - Part 3 Ex 11.4, 3 - Chapter 11 Class 7 Perimeter and Area - Part 4

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Question 3 A picture is painted on a cardboard 8 cm long and 5 cm wide such that there is a margin of 1.5 cm along each of its sides. Find the total area of the margin. Here, Area of margin = Area of larger rectangle − Area of smaller rectangle Finding length and breadth of both rectangles Larger rectangle Length of larger rectangle = 8 m Breadth of larger rectangle = 5 m Smaller Rectangle There is 1.5 cm margin left all around the cardboard ∴ Length of smaller rectangle = Length of larger rectangle – 2 × 1.5 = 8 − 3 = 5 m Breadth of smaller rectangle = Breadth of smaller rectangle – 2 × 1.5 = 5 − 3 = 2 cm Larger rectangle Length = l = 8 m Breadth = b = 5 m Area of larger rectangle = l × b = 8 × 5 = 40 cm2 Smaller rectangle Length = l = 5 cm Breadth = b = 2 cm Area of smaller rectangle = l × b = 5 × 2 = 10 cm2 Now, Area of margin = Area of larger rectangle − Area of smaller rectangle = 40 − 10 = 30 cm2 ∴ Area of margin is 30 cm2

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Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 13 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.