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Q.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.
Answer :

Length = 8 cm, breadth = 5 cm
Area of the cardboard = l × b \( = 8 cm × 5 cm = 40 cm^2\)
Width of the margin = 1.5 cm
Length of the inner cardboard= 8 cm – 1.5 × 2 cm
= 8 cm – 3 cm = 5 cm
Breadth of the inner cardboard= 5 cm – 1.5 × 2 cm
= 5 cm – 3 cm = 2 cm
Area of the inner rectangle = l × b
= 5 cm × 2 cm = 10 \(cm^2 \)
Area of the margin\(= 40 cm^2 – 10 cm^2 = 30 cm^2 \) Hence, the required area = 30\( cm^2\)