If the diameter of a wire is decreased by

What will come in place of the question mark (?) in the following series?

168, 120, ?, 48, 24, 8

120, 126, 138, 162, ?, 306

In each of the following number series, one term is missing. Find the missing term.

121, 100, 81, ?, 49, 36

84, 105, ?,  168, 210, 259

480, 288, ?, 103.68, 62.208, 37.3248

42, 48, 60, 84, 132, ?

What will come in place of the question mark (?) in the following number series?

21, 42, 67, 96, ?, 166

11           20           ?              64           112         192

14, 17, 23, 32, ?, 59