Find the missing term in the series.
?, 132, 165, 204, 249

The correct answer is 105.

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

Let the missing term be represented by x.

The series is: x, 132, 165, 204, 249

First, calculate the differences between adjacent known terms:

165 - 132 = 33

204 - 165 = 39

249 - 204 = 45

Now, observe the pattern in the differences:

39 - 33 = 6

45 - 39 = 6

The difference between consecutive terms increases by 6 each time. Following this pattern backwards:

The difference before 33 should be:

$33-6=27$

Therefore, the difference between the second term (132) and the first term (x) is 27:

$132-x=27$

$x=132-27$

$x=105$

Thus, the missing term in the series is 105.