Q1 of 32 Page 260

An iron pillar consists of a cylindrical portion of 2.8 m. height and 20 cm. in diameter and a cone of 42 cm. height surmounting it. Find the weight of the pillar if 1cm3 of iron weighs 7.5 g.


Given that, height of cylinder(H) = 2.8m = 280 cm, diameter(d) is 20 cm and height of cone(h) is 42 cm.


⇒ radius(r)


⇒ vol. of pole = vol. of cylinder + vol. of cone






= 92400 cm3


If 1 cm3 of iron weighs 7.5 g.


⇒ the weight of the pillar = 92400 × 7.5


= 693,000 g


= 693 kg (∵ 1kg = 1000g)


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