Question

An iron pillar consists of a cylindrical portion of 2.8 m.height and 10cm.in radius and cone of 42cm.height surmounting it . Find the weight of the pillar if 1cm cube o f iron weight 75gm.

Answer 1

$volume \: of \: cylinder = \pi {r}^{2} h \\ = \frac{22}{7} \times ( {10}^{2} ) \times 280 = 88000 \: {cm}^{3}$
$volume \: of \: cone = \frac{1}{3} \pi {r}^{2} h \\ = \frac{1}{3} \times \frac{22}{7} \times {10}^{2} \times 42 = 4400 \: {cm}^{3}$
$weight \: of \: pillar \: = total \: volume \\ \times \: density \\ = 92400 \times 75 = 6930 \: kg$