Surface and Area

Q 1: In a shower, 4 cm of rain falls. The volume of water that falls on 1 hectares of ground is: A)450 m3 B)400 m3 C)300 m3 D)None of these Answer : Option B Explanation: 1 hectare = 10,000 m2 So, Area = (1 x 10000) m2 = 10000 m2. Depth=(4/100)m=(1/25)m Volume = (Area x Depth) =[10000 x(1/25)]m3=400 m3 Q 2: How many bricks, each measuring 20 cm x 11.25 cm x 4 cm, will be needed to build a wall of 5 m x 6 m x 22.5 cm? A)7500 B)6500 C)7540 D)None of these Answer : Option A Explanation: Number of bricks =(Volume of the wall)/Volume of 1 brick =(500 x 600 x 22.5)/(20 x 11.25 x 4)=7500 Q 3: A cistern 6m long and 2 m wide contains water up to a depth of 1 m 25 cm. The total area of the wet surface is: A)42 m2. B)22 m2. C)35 m2. D)32 m2. Answer : Option D Explanation: Area of the wet surface = [2(lb + bh + lh) - lb] = 2(bh + lh) + lb = [2 (2 x 1.25 + 6 x 1.25) + 6 x 2] m2 = 32 m2. Q 4: What is the height of a circular cone? A: The area of that cone is equal to the area of a rectangle whose length is 33 cm. B: The area of the base of that cone is 154 sq. cm. A)Both A and B are not sufficient to answer B)A alone sufficient while B alone not sufficient to answer C)Both A and B are necessary to answer D)None of these Answer : Option A Explanation: B gives the value of r. But, in A, the breadth of rectangle is not given. So, we cannot find the surface area of the cone. Hence, the height of the cone cannot be determined. Correct Answer is Option A.

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