Which of the following numbers will replace the question mark (?) in the given series?

11, 36, ?, 121, 185, 266

To find the missing number in the series, let us analyze the differences between consecutive terms.

The given series is: 11, 36, ?, 121, 185, 266.

Let us look at the differences between the known consecutive terms at the end of the series:

Difference between 185 and 121: $185-121=64$

Difference between 266 and 185: $266-185=81$

We notice that these differences are consecutive perfect squares:

$64=8^2$

$81=9^2$

Following this pattern of adding consecutive squared numbers, the differences between consecutive terms should be:

1st difference: $5^2=25$

2nd difference: $6^2=36$

3rd difference: $7^2=49$

4th difference: $8^2=64$

5th difference: $9^2=81$

Let's verify this hypothesis with the first transition:

$11+25=36$ (which matches the second term in the series).

Using the pattern, the missing term (?) is obtained by adding $6^2=36$ to the second term (36):

$36+36=72$

Let's check if adding $7^2=49$ to this result yields the next term in the series (121):

$72+49=121$

Since the pattern holds true, the number that replaces the question mark is 72.