If the circumference of a circle increases form 4 π to 8 π, what change occurs in its area? · ABC26GN4655
Subject: General Aptitude · Chapter: Area
If the circumference of a circle increases form $4 \pi$ to $8 \pi$, what change occurs in its area?
(a)It is halved.
(b)It doubles.
(c)it triples.
(d)It quadruples.
Answer
Answer (as printed): D
Explanation
$2 \pi R_{1}=4 \pi$ and $2 \pi R_{2}=8 \pi \quad \Rightarrow \quad R_{1}=2$ and $R_{2}=4$ ⇒ Original area $=\left(4 \pi \times 2^{2}\right)=16 \pi$, Increased area $=\left(4 \pi \times 4^{2}\right)=64 \pi$. Thus, the area quadruples.
Explanation as extracted from the printed page; notation may be imperfect.