A cylindrical jar of radius 6 cm contains oil. Iron spheres each of radius 1.5 cm are immersed in the oil. How many spheres are necessary to raise the level of the oil by two centimeters?
Given that, radius of cylindrical jar, r = 6cm
Depth/height of the jar, h = 2cm
Volume of the jar, V’ = π r2 h
⇒ V’ = π (6)2 (2) cm3
Radius of the sphere = 1.5cm
So, volume of the sphere = 
Volume of oil in cylindrical jar = volume of n spheres needed to raise the level by 2 cm
⇒ n = 16
∴ number of iron sphere needed = 16
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