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# A cylindrical roller made of iron is 2 m long. Its inner diameter is 35 cm and the thickness is 7 cm all round. Find the weight of the roller in kg, if 1 cm3 of iron weighs 8 g.

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M.L Aggarwal book Important Question of class 10 chapter Based on Mensuration for ICSE BOARD.
A cylindrical roller made of iron is 2 m long. Its inner diameter and the thickness is given .
Find the weight of the roller in kg, if 1 cm3 of iron weighs 8 g.
This is the Question Number 22, Exercise 17.1 of M.L Aggarwal.

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1. Length of the roller, h = 2 m = 200 cm [1m = 100 cm]

Inner diameter = 35 cm

Inner radius, r = 35/2 cm

Thickness = 7 cm

= (35+14)/2

= 49/2 cm

Volume of the iron in roller = π(R2-r2)h

= (22/7)[( 49/2)2-(35/2)2]200

= (22/7)[( 492-352/4]200

= (22/7)×50( 492-352)

= (22/7)×50( 492-352)

= (22/7)×50 (2401-1225)

= (22/7)×50×1176

= 184800 cm3

Given 1 cm³ of iron weighs 8 g.

Weight of the roller = 184800×8 = 1478400 g

= 1478.4 kg [1 kg = 1000 g]

Hence the weight of the roller is 1478.4 kg.

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