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30 Mar 2008 08:55:35 IST

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how to find volume of parallelopiped if diagonals are given instead of its edges!

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Q. One of the diagonals of a parallelopiped is 4j-8k. If the two diagonals of one of its faces are 6i+6k and 4j+2k, then its volume is

a) 60

b) 80

c) 100

d) 120

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pink_ele

Blazing goIITian

Joined: 16 Jan 2007

Posts: 1836

30 Mar 2008 18:30:34 IST

Like 2 people liked this

let a+b+c=4j-8k
a+b=6i+6k
a-b=4j+2k,
get a b n c as
a=3i+2j+4k
b=3i-2j+2k
c=-6i+4j-14k
thus vol is scalar triple product of abc

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