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 the transitions between consecutive terms in the series:
300, ?, 148, 221, 441, 1101.5

The pattern involves multiplying each term by a progressively increasing multiplier (starting from 0.5 and increasing by 0.5 at each step) and then subtracting 1 from the result.

Let us denote the terms of the series as $T_1,T_2,T_3,T_4,T_5,T_6$.

Following this pattern:

$T_2=(T_1\times 0.5)-1$
$T_2=(300\times 0.5)-1=150-1=149$

Now, let us verify if the subsequent terms follow the same rule:

For the third term:
$T_3=(T_2\times 1.0)-1=(149\times 1)-1=148$

For the fourth term:
$T_4=(T_3\times 1.5)-1=(148\times 1.5)-1=222-1=221$

For the fifth term:
$T_5=(T_4\times 2.0)-1=(221\times 2)-1=442-1=441$

For the sixth term:
$T_6=(T_5\times 2.5)-1=(441\times 2.5)-1=1102.5-1=1101.5$

Since the pattern perfectly holds true for all numbers in the series, the missing term is 149.

Therefore, the correct option is 149.