PrepRung
Sign inSign up free

NDA 2018 Maths · Mathematics · Three Dimensional Geometry · easy

The plane z=3 cuts the sphere x^2+y^2+z^2=25 in a circle of radius

Single correct option

The plane z=3z=3 cuts the sphere x2+y2+z2=25x^2+y^2+z^2=25 in a circle of radius
  1. A. 44
  2. B. 55
  3. C. 33
  4. D. 34\sqrt{34}
Show answer and solution

Answer: (A) 44

On the plane z=3z=3 the equation becomes x2+y2=25−9=16x^2+y^2=25-9=16, a circle of radius 44. The sphere's radius 5 is the trap; the section radius is R2−d2\sqrt{R^2-d^2} with d=3d=3 the distance of the centre from the plane.
Report a mistake

Original question written in the NDA 2018 Maths pattern and checked twice for the correct answer. Not an official question paper. How we write and check questions · Corrections policy · Report a mistake