Q2 of 110 Page 65

The 8th term of the sequence 1, 1, 2, 3, 5, 8, g is

The above series is also called a Fibonacci sequence, where each term is the sum of its preceding two terms.


an = an-1 + an-2


We are interested in 8th term so substituting n = 8 in the above equation,


a8 = a7 + a6. Also, a7 = a6 + a5


a8 = (a6 + a5) + a6


a8 = (8 + 5) + 8


a8 = 21


So the correct option is D.

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