Question

which number replace (?)and how

6, 9, 15, 27, ? ​

Answer 1

We need to recall the following definitions to solve the problem.

Sequence:

An ordered list of numbers (or other items like as geometric objects) that often follow a specified pattern or function is known as a sequence.

This problem is about the series.

Given series is 6, 9, 15, 27, ? ​.

We have to find the number which replace "?".

Determine the pattern

First term $3 + 2^0(3) = 6,$

Second term $3 + 2^1(3) = 9$,

Third term $3 + 2^2(3) = 15$,

Fourth term $3 + 2^3(3) = 27,$

Then the sequence is $3 + 2^{n-1}(3) = 6,$

where n is term number.

So fifth term is $3 + 2^4(3) = 81$.

Hence the number is 81.

Answer 2

We must recall that:

Sequences are the grouped arrangement of numbers orderly and according to some specific rules.

Given:

$6,9,15,27,...$

$6\times2-3=9\\9\times2-3=15\\15\times2-3=27\\27\times2-3=51$

Hence answer is $51.$