Final answer:
The missing number in the sequence cannot be determined without additional context or information, as the sequence does not follow a discernible pattern with the given numbers. Further clarification is needed to answer accurately.
Step-by-step explanation:
The number missing in the sequence 17.2, 84, 13.5, V, 45 is not clearly based on a numerical pattern that is discernible from the given numbers alone. Typically, sequences follow a certain rule or pattern, whether that involves addition, subtraction, multiplication, division, or some other mathematical operation between the terms. However, without a clear pattern or additional context, it is not possible to determine what V represents in the sequence.
It is important to consider if there has been a typo, or if more information is needed to correctly ascertain the missing number. The sequence provided does not fit a common numerical pattern, and the other potential options provided (a) 2, (b) 3, (c) V45, (d) .2 do not seem to correspond to any clear rule when applied to the existing numbers in the sequence. Therefore, without further context or clarification, we cannot provide a definitive answer to this question.