Question

18. If log (3 + 4 + k) = log 3 + log 4 + log k, then the
value of k is
(a)11/7
(b) 7/11
(c) 7 x 11
(d) None of these
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Answer 1

Hey Buddy

Here's the answer

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# Some important identities

1. log m + log n = log mn

2. log m - log n = log m/n

=> log (3 + 4 + k) = log 3 + log 4 + log k

using identity ( 1 )

=> log ( 3 + 4 + K ) = log ( 3×4×K )

=> log ( 7 + K ) = log ( 12 K )

taking antilog both sides

=> 7 + K = 12 K

=> 12 K - K = 7

=> 11 K = 7

=> K = 7/11

Hence option ( b ) is correct

HOPE HELPED

PEACE :)

Answer 2

log( 7+k ) = log ( 3.4.K)

7+ K = 12k

11K = 7

k = 7/11

b is correct