Lethal dose require to reduce the population by half of

Given set:  [99, 200, 301]

If ‘534’ = ‘50’, ‘758’ = ‘138’, ‘3156’ = ‘71, then ‘4738’ = ?

Which of the following will best complete the relationship given below?

HOST: 28 :: LENT: ? :: BACK: 13

Select the combination of letters that when sequentially placed in the blanks of the given letter series will complete the series.

Select the option in which the numbers share the same relationship as that shared by the given number-pair:

144 : 156

E × I : 25 × 81 ∷ K × P : ?

Select the option that is related to third letter cluster in the same way as the second letter cluster is related to the first letter cluster.

Horse: Filly:: Cockroach:?