Total number of letters in the word MONDAY is 6.
Number of vowels are 2(O,A)
Six letters word is to be formed.
□□□□□□
First letter should be a vowel. So, the rightmost place of the words formed can be filled only in 2 ways.
Since the letters cannot be repeated , the second place can be filled by the remaining 5 letters. So, second place can be done in 5 ways
Similarly, third place in 4 ways , fourth place in 3 ways, fifth place in 2 ways, sixth place in 1 way.
Hence, required number of words that can be formed using four letters of the given word is 2×5×4×3×2×1=240