Subject: General Aptitude · Chapter: Volume and Surface Area · Exam: · Marks: · Difficulty:
If the height of a right circular cone is increased by 200% and the radius of the base is reduced by 50%, then the volume of the cone [CDS, 2016] 791
(a)remains unaltered
(b)decrease by 25%
(c)increase by 25%
(d)increase by 50%
Answer
Answer (as printed): B
Explanation
Let the radius of a right circular cone be R cm and height be H cm. 1 2 Volume of right circular cone = πR H cu.cm. 3 When height of right circular cone is increased by 200% and radius of the base is reduced by 50%. 2 1 R New volume = π ⋅ 3H 3 2 QUANTITATIVE APTITUDE 1 R2 4 πR 2 H = π ⋅ 3H = 3 4 4 2 1 1 1 2 Difference = πR H − = πR H 3 4 12 1 πR 2 H Decrease percentage = 12 × 100 = 25% 1 2 πR H 3
Explanation as extracted from the printed page; notation may be imperfect.