Question

What is the 5th number statements: 1st and 2nd numbers are 1 and 2 respectively?

Answer 1

Given statements: 1st and 2nd numbers are 1 and 2 respectively.
the 5th number is 5

Answer 2

Answer:  The answer is 5 or 16.

Step-by-step explanation: We are given to find the fifth number, where the first and second numbers are 1 and 2 respectively.

We will consider the following two cases to find the fifth number which includes addition and multiplication.

(i) Let the sequence be A.P. (an arithmetic progression). Then the first term will be a = 1 and common difference will also be d = 1. In this case the 5th number will be

$a_5=a+(5-1)d=1+4\times 1=5.$

(ii) Let the sequence be G.P. (a geometric progression). Then the first term will be a = 1 and common ratio will be r = 2. Here, the 5th number will be

$a_5=ar^{5-1}=1\times 2^4=16.$

Thus, the 5th number can be 5 or 16.