Question

An iron pillar consists of a cylindrical portion $2.8m$ high and $20cm$ in diameter and a cone $42cm$ high is surrounding it. Find the weight of the pillar, given that $1$cubic $cm$ of iron weights $7.5gm$.

Answer 1

Volume of pillar$=\pi r^2.H+\frac{1}{3}\pi r^{2}h=\pi r^2[H+\frac{h}{3}]$

$=\frac{22}{7}\times 10\times 10[280+\frac{42}{3}]$

$=\frac{22}{7}\times 100\times 294=92400c{m}^3$

$1㎤$ weighs$=7.5g$

$92400㎤$ weighs$=7.5\times 92400=693000g=693kg$