We have,
There are 3 vowels and 3 other letters as the 3 vowels are to be together,
Consider them as one object.
Therefore there are 4 objects totally, which can be arranged in 4!ways,but the vowels can be arranged internally in 3! ways.
Therefore total no, of ways of arranging the word with the vowels together is 4!×3!=24×6=144
That is no, of word with vowels together is 144.
But the total number of random arrangement are =6!=720
Required probability =720144=15