A cylindrical pillar has diameter $0.7$ m and height $5$ m. Find its CSA. Use $\pi=\dfrac{22}{7}$.

A cylindrical pillar has diameter $0.7$ m and height $5$ m. Find its CSA. Use $\pi=\dfrac{22}{7}$.
  1. $11 \text{ m}^{2}$
  2. $22 \text{ m}^{2}$
  3. $5.5 \text{ m}^{2}$
  4. $15.4 \text{ m}^{2}$

Solution

$r = 0.35$ m. CSA $= 2\pi r h = 2 \times \dfrac{22}{7} \times 0.35 \times 5 = \dfrac{44}{7} \times 1.75 = \dfrac{77}{7} = 11 \text{ m}^{2}$.

Asked in: IMO

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