Find out the missing term of the number series given below.

300, ?, 148, 221, 441, 1101.5

To find the missing term of the number series, let us analyze the pattern of operations between consecutive terms in the series:
300, ?, 148, 221, 441, 1101.5

Let us look at the transition from the third term to the fourth term:
$148\times 1.5-1=222-1=221$

Now, let us examine the transition from the fourth term to the fifth term:
$221\times 2-1=442-1=441$

Next, let us look at the transition from the fifth term to the sixth term:
$441\times 2.5-1=1102.5-1=1101.5$

From the above transitions, we can observe that the pattern for the n-th term is:
${\text{Term}}_n=({\text{Term}}_{n-1}\times \text{Multiplier})-1$
where the multipliers increase by 0.5 at each step (i.e., 0.5, 1.0, 1.5, 2.0, 2.5, ...).

Following this logical pattern, let us calculate the missing second term by applying the first multiplier of 0.5 to the first term (300):
$300\times 0.5-1=150-1=149$

To verify, we can apply the next multiplier of 1.0 to this missing term (149) to see if we get the third term (148):
$149\times 1.0-1=149-1=148$

This matches the third term of the series exactly. Therefore, the missing term is 149.