A solid iron dumb-bell is made of two spheres of radius 2.1 cm joined by a cylindrical bar of radius 1.4 cm and length 10 cm. Find the volume of iron used, in cubic centimetres, correct to two decimals. (Take π = 22/7.)

Question

Accepted Answer

139.22. One sphere = 4/3\π (2.1)^3 = 4/3 × 22/7 × 9.261 = 38.808 cm³, so two = 77.62 cm³. Bar = \π r^2 h = 22/7(1.96)(10) = 61.6 cm³. Total = 77.62 + 61.6 = 139.22 cm³. 100.41 counts only one sphere; 61.6 is the bar alone; 77.62 is the two spheres alone.

A solid iron dumb-bell is made of two spheres of radius 2.1 cm joined by a cylindrical bar of radius 1.4 cm and length 10 cm. Find the volume of iron used, in cubic centimetres, correct to two decimals. (Take π = 22/7.)

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