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Question
If ‘V’ is the volume of a cuboid of dimensions a × b × c and ‘S’ is its surface area, then prove that: `1/V = 2/S[1/a +1/b + 1/c]`
Solution
The volume (V) of a cuboid = a x b x c
`:. 1/V = 1/(abc)` .......(1)
The surface area (S) of a cuboid = 2(ab + bc + ca) .....(2)
`2/S = 1/(ab+bc+ac)`
RHS = `2/S (1/a + 1/b + 1/c)= 1/(ab +bc+ac)(1/a+1/b+1/c)`
`2/S xx (1/a+1/b+1/c) = 1/(abc)`
`:. 2/S xx(1/a+ 1/b + 1/c)= 1/V`
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