Which of the following numbers will replace the question mark (?) in the given series?
15, ?, 27, 39, 55, 75

How many pairs of consecutive numbers are there in the following number sequence each of which is in ascending order (Like 1, 2)?
7 6 7 8 6 7 5 6 8 7 7 8 6 5 4 5 6 3 4

Select the number from among the given options that can replace the question mark (?) in the following series.
36, 75, 147, 297, 591, ?

In the following question, select the missing number from the given series.
4, 15, 2, 17, ?, 19