MCQ
The number of solid sphere each $6\ cm$ in diameter, which can be moulded from a solid cylinder of height $45\ cm$ and diameter $4\ cm$ without any loss, is:
  • $5$
  • B
    $10$
  • C
    $7$
  • D
    $12$

Answer

Correct option: A.
$5$

Given, diameter of ball $= 6\ cm$ and diameter of cylinder $= 4\ cm$
So, radius of ball, $R = 3\ cm$ Radius of cylinder, $r = 2\ cm$
Let the number of balls be $ n$
So, volume of $n$ balls $=$ volume of a cylinder
$\text{n}\times\frac{4}{3}\pi\text{R}^3=\pi\text{r}^2\text{h}$
$\text{n}\times\frac{4}{3}\times27=4\times45$
$\text{n}=\frac{4\times45}{4\times9}$
$\text{n}=5$

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