Verbal Reasoning - Mental Ability Questions

Choose the correct alternative which will complete the following series:

21, 55, 19, 50, 17, 45, ?

Select the related word/letters/number from the given alternatives.

PZQW : NXOU :: FISK : ?

Select the related word from the given alternatives.

Night : Stars :: Day : ?

Select the related word/letters/number from the given alternatives.

23 : 6 : : 43 : ?

Select the related word/letters/numbers from the given alternatives:

15 : 225 : : 12 : ?

In the following question, select the related number from the given alternatives.

63 : 105 : : 48 : ?

Select the related word/letters/numbers from the given alternatives:

DHL : PTX :: BFJ : ?

Select the related number from the given alternatives.

10 : 1000 :: 2 : ?