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Question
A pen stand made of wood is in the shape of a cuboid with four conical depressions to hold pens. The dimensions of the cuboids are 15 cm by 10 cm by 3.5 cm. The radius of each of the depressions is 0.5 cm and the depth is 1.4 cm. Find the volume of wood in the entire stand (see the following figure). Use [π = `22/7`]
Solution
Depth (h) of each conical depression = 1.4 cm
Radius (r) of each conical depression = 0.5 cm
Volume of wood = Volume of cuboid − 4 × Volume of cones
= `"lbh" - 4 xx 1/3pir^2h`
`= 15 xx 10 xx 3.5 - 4 xx 1/3 xx 22/7 xx (1/2)^2 xx 1.4`
= 525 – 1.47
= 523.53 cm3
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