The absolute refractive index of ______ is

8, ?, 29, 57, 113, 225

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

15, 26, 39, 56, ?, 98

321,  240,  ?,  105,  51,  6

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

7, 14, 28, 56, 112, ?

9       14       38       129       ?      2705      16260

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


11, 18, 32, 60, ?, 228

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

7, 84, 69, 828, 813, ?

What should come in place of (?) question mark in the given number series.

3, 8, 18, 38, 78, ?

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

17, 21, 30, 46, ?, 107

97, 106, ?, 195, 411, 460