NIACL Model Paper 5 with solutions for free online practice

The word SIGNATURE consists of nine letters comprising four vowels (A, E, I and U) and five consonants (G N, R, T and S). When the four vowals are considered as one letter, we have six letters which can be arranged in ${}_{}^6{\mathit{P}}_6^{}$ ways i.e., 6! ways. Note that the four vowels can be arranged in 4!
Hence, required number of words = $6!\times 4!=720\times 24=17280$