Find the missing number in the series:5 15 9 ? 11 33 13 39

The correct answer is Option (3) → 27

The numbers go in pairs, and in each pair the second number is three times the first:

• 5 and 15: \(5\times3=15\)

• 9 and ?: \(9\times3=27\)

• 11 and 33: \(11\times3=33\)

• 13 and 39: \(13\times3=39\)