A plate of 5m x 2m size with uniform thickness, weighing 20 kg, is perforated with 1000 holes of 5cm x 2cm size. What is the weight of the plate (in kg) after perforation?
Given:
Original plate size = 5 m × 2 m = 10 m²
Weight before perforation = 20 kg
Each hole = 5 cm × 2 cm = 0.05 m × 0.02 m = 0.001 m²
Number of holes = 1000
Total area removed = 1000 × 0.001 m² = 1 m²
Concept Used:
Weight is proportional to area (since thickness is uniform).
Formula Used:
New weight = Original weight × (Remaining area / Original area)
Solution:
Remaining area = 10 m² – 1 m² = 9 m²
New weight = 20 × (9 / 10) = 18 kg
Correct Option: (D) 18kg
The curved surface area of a cylinder having radius 5 cm and height 23 cm is:
Nine identical cubes, each with edge 3 cm, are joined in a straight line to form a cuboid. What is the total surface area (in cm²) of the resulting cuboid?
The surface area of a cube is 480 Find its volume.
The parallel sides of a trapezium are 48 cm and 20 cm. Its non-parallel sides are 26 cm and 30 cm. What is the area (in cm²) of the trapezium?
A circle is inscribed in a triangle with sides 28 cm, 45 cm and 53 cm. What is the area of the triangle excluding the area of the circle? (Use π = 3.14)
A cubical tank with side 50 cm is full of water. If 61 litres of water is taken out of it, the level of water in the tank will drop by:
The cost of polishing the total surface area of a solid cone at ₹ 0.50 per cm² is ₹ 5632, and the circumference of its base is 176 cm. What is the height of the cone? (Use π = 22/7)
The curved surface area of a solid metallic right circular cylinder is 1792π cm² and its base radius is 32 cm. It is melted and recast into 42 solid spherical balls of equal radius. What is the surface area (in cm²) of a ball ?
