Arrange the following words according to the dictionary ?
1. Inventory 2. Involuntary 3. Invisible 4. Invariable 5. Investigate

Since the first three alphabets of all the words are inv, we need to start checking with the fourth alphabet.
4th word has 'a' as the fourth alphabet so it is the first in the order.
1st and 5th have 'e' as their fourth letter, so we have to check their fifth letters which are 'n' and 's'.
'n' comes before 's', hence it is second in the order and fifth is third in the order.
In the 3rd word 'i' is the fourth letter and it comes fourth in the order.

Hence the required order is 4,1,5,3,2