Question

The ${8^{{\text{th}}}}$ term of the sequence 1, 1, 2, 3, 5, 8 …….is
$
  {\text{A}}{\text{. 25}} \\
  {\text{B}}{\text{. 24}} \\
  {\text{C}}{\text{. 23}} \\
  {\text{D}}{\text{. 21}} \\
$

Answer 1

Hint – To find the eighth term, we identify the given sequence as a Fibonacci series. Using its condition we find the ${8^{{\text{th}}}}$ term.

Step-by-step answer:
Here the given sequence,
1, 1, 2, 3, 5, 8 is a Fibonacci sequence.

Fibonacci sequence is a series of numbers in which each number (Fibonacci number) is the sum of the two preceding numbers.

As,
2 = 1+1
3 = 1+2
5 = 2+3
8 = 3+5


Therefore, next (${7^{{\text{th}}}}$) term = Sum of the previous two terms = 5 + 8 = 13


Hence, ${8^{{\text{th}}}}$ term = 8 + 13 = 21.

Option D is the correct answer.

Note: The key in solving such kind of problems is to identify the kind of sequence given in this case is a Fibonacci Series and to know its definition.
Fibonacci Series typically starts from 0 or 1.