1, 5, 13,25,41,?

Each number in the series is 2 less than thrice the preceding number.

So, missing number = (10 x 3) - 2 = 28.

Each number in the series is one more than twice the preceding number.

So, missing term = (15 x 2) + 1 = 31.

The given sequence is a combination of three series :

I. 1st, 4th, 7th, 10th terms i.e. 8, 7, 6, ?

II. 2nd, 5th, 8th, 11th terms i.e. 9, 10, 11, 12

III. 3rd, 6th, 9th terms i.e. 8, 9, 10 The pattern in I is - 1.

So, missing term = 6 - 1 = 5.

Clearly, 5 + 3 = 8, 8 + 3 = 11, 11 + 3 = 14, .....

So, the series is an A.P. in which a - 5 and d = 3.

Let 320 be the nth term of the series.

Then, 320 = 5 + (n - 1) x 3 or (n - 1) = 105 or n = 106.

The pattern is x 3.

So, missing term = 108 x 3 = 324.

The pattern is - 66, - 55, - 44, - 33, - 22, .....

So, missing term = 105 - 11 = 94.

The pattern is + 3, + 5, + 7, + 9, .....

So, missing term = 28 + 11 = 39.

The pattern is ÷ 6, ÷ 5, ÷ 4, ÷ 3, ÷ 2.

So, missing term = 960 - 5 = 192.

The given sequence is a combination of two series:

I. 45, 47, 49, 51, 53 and II. 54, ?, 56, 57

Clearly, II consists of consecutive natural numbers, starting from 54.

So, missing term = 55.

The pattern followed is : nth term + (n + l)th term + (n + 1) = (n + 2)th term.

Thus, 1st term + 2nd term + 2 = 3rd term; 2nd term + 3rd term + 3 = 4th term and so on.

So, missing term = 6th term = 4th term + 5th term + 5 = 24 + 41 + 5 = 70.