Areas
Practice Questions - Areas
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Q1) Find the area of the sector of a circle whose radius is 14 cm and angle of the sector is 45 degrees. 1) 77 cm2 2) 38.5 cm2 3) 19.25 cm2 4) 154 cm2 Area of sector of radius 14 cm and 45 degrees as the central angle = (22/7)×142×(45/360) = 77 cm2 Hence, option 1. Q2) Area of a rectangle is 144 cm2. Its breadth is 9 cm. Find its length. 1) 14 cm 2) 12 cm 3) 16 cm 4) 18 cm Let L be the length of the rectangle. ATQ, 9L = 144 L = 16 cm Hence, option 3. Q3) Ratio of length and perimeter of a rectangular plot is 2:5. What is the ratio of length and breadth of the plot? 1) 4:1 2) 3:1 3) 2:1 4) 3:2
As, the ratio of length and perimeter of a rectangular plot is 2:5 So, let us suppose that length is 2 units and Perimeter is 5 units Perimeter of a rectangle = 2(L + B) ∴ 5 = 2(2 + b) On solving, b = 1/2 Ratio of length and breadth of the plot = 2/(1/2)=4 Hence, option 1. Q4) If radius of a circle is increased by 20%, find the percentage change in area? 1) 40% 2) 20% 3) 44% 4) 22%
Let the initial radius be 1 unit. Initial area = π(1)2 = π (radius = 1 unit) Radius of a circle is increased by 20% ∴ New radius = 1.2 units Final area = π(1.2)2 = 1.44π Percentage Change in Area  Change in Area = Final Area - Initial Area = 1.44π - π = 0.44π Percentage Change in Area  Hence, option 3. |