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If a¯=3i^+j^+4k^,b¯=2i^-3j^+λk^,c¯=i^+2j^-4k^ and a¯.(b¯×c¯)=47, then λ is equal to ______ -

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Question

If `overlinea = 3hati + hatj + 4hatk, overlineb = 2hati - 3hatj + lambdahatk, overlinec = hati + 2hatj - 4hatk` and `overlinea.(overlineb xx overlinec) = 47`, then λ is equal to ______

Options

  • 4

  • 5

  • 6

  • 7

MCQ
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Solution

If `overlinea = 3hati + hatj + 4hatk, overlineb = 2hati - 3hatj + lambdahatk, overlinec = hati + 2hatj - 4hatk` and `overlinea.(overlineb xx overlinec) = 47`, then λ is equal to 5.

Explanation:

`overlinea.(overlineb xx overlinec) = 47`

∴ `|(3, 1, 4), (2, -3, lambda), (1, 2, -4)| = 47`

⇒ 3(12 - 2λ) - 1(-8 - λ) + 4(4 + 3) = 47

⇒ λ = 5

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