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📐 Mathematics  ·  Circles & Mensuration  ·  JEE

The angle subtended by a chord at centre is 90°. If chord = 10 cm, radius =

Answer: 5√2 cm.

  • A 5√2 cm
  • B 5 cm
  • C 10 cm
  • D 7 cm

Correct answer: A. 5√2 cm

Explanation: Triangle is right-angled isosceles. Chord² = r² + r² = 2r². 100 = 2r². r = 5√2 cm.

Cylinder, Cone, SphereV=πr²hCSA=2πrhV=⅓πr²hCSA=πrlV=4/3πr³SA=4πr²

Three standard 3D solids and their key formulas: a cylinder's volume scales with the full height, a cone's volume is exactly one-third of the cylinder with the same base and height, and a sphere's volume and surface area both follow distinct r-based formulas worth memorising separately.

Concept context

Perimeters, areas, and volumes of 2D and 3D shapes

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