Question

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

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.