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Class 10 › Mathematics › Surface Areas and Volumes
CBSE2026Class Class 10 · Mathematics1 Marks · Mcq✅ Verified
Three tennis balls are just packed in a cylindrical jar. If radius of each ball is $r$, volume of air inside the jar is
A. $2\pi r^3$
B. $3\pi r^3$
C. $5\pi r^3$
D. $4\pi r^3$
✅ Answer & Solution
✅ Correct Answer: A
Step 1: The balls just fit, so radius of jar $=r$ and height of jar $=3\times 2r=6r$.
Step 2: Volume of cylinder $=\pi r^2 h=\pi r^2(6r)=6\pi r^3$.
Step 3: Volume of 3 balls $=3\times\dfrac{4}{3}\pi r^3=4\pi r^3$.
Step 4: Volume of air $=$ Volume of jar $-$ Volume of balls
$$=6\pi r^3-4\pi r^3=2\pi r^3$$
Answer: (A)
