Latest CAT Aptitude Question SOLUTION: For a Fibonacci sequence, from the third term onwards, each term in the sequence is the sum of the previous two terms in that sequence. If the difference of squares of seventh and

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(#M40013906) CAT question fibonacci series Keep an EYE

For a Fibonacci sequence, from the third term onwards, each
term in the sequence is the sum of the previous two terms in that sequence.
If the difference of squares of seventh and sixth terms of this sequence is
517, what is the tenth term of this sequence?
(a) 147 (b) 76
(c) 123 (d) Cannot be determined

Asked In CAT sc mandota (11 years ago)

Solved HARMEET KAUR Read Solution (3)

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HARMEET KAUR  (11 years ago)

(a7)^2 - (a6)^2 = 517
(a7 + a6)(a7 - a6) = 47*11

a7 +a6 = 47
a7 - a6 = 11 = a5

a5=11
a6 = 18
a7 = 29
a8 = 47
a9 = 76
so
a10= 123

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HARMEET KAUR  (11 years ago)

If we consider
(a7)^2 - (a6)^2 = 517
(a7 + a6)(a7 - a6) = 47*11 = 517*1 = (-47)*(-11) = (-1)*(-517)

then answer will be different.

If negative numbers in series are allowed ( which are not allowed in normal finonacci sequence),

tenth term can not be unique.
Then can not be determined.

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HARMEET KAUR  (11 years ago)

Fibonacci sequence can have negative numbers as per link below...

http://en.wikipedia.org/wiki/Generalizations_of_Fibonacci_numbers

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