Zaymiey

📐 Mathematics  ·  Circles & Mensuration  ·  JEE

The circles x² + y² = 9 and x² + y² − 8x + 7 = 0 are:

Answer: Intersecting at two points.

  • A Touching externally
  • B Intersecting at two points
  • C One inside the other
  • D Concentric

Correct answer: B. Intersecting at two points

Explanation: Centres (0,0) and (4,0), both radius 3, distance 4. Since |3−3| < 4 < 3+3, they intersect at two points.

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

Read the full Circles & Mensuration notes →