The number of five letter words containing 3 vowels and 2 consonants that can be formed using the letters of the word EQUATION so that two constants occur together is

Vowels (A,E,I,O,U) five, consonants (Q,T,N) three  

(i) 3 vowels can be chosen in ${ }^5{\mathrm{C}}_3$ ways
(ii) 2 consonants can be chosen in ${ }^3{\mathrm{C}}_2$ ways
(iii) 2 consonants can be bundled in 2! ways
(iv) 3 vowels + (2 consonants bundle) : can be arranged in 4! ways. 

$\therefore$ Required number of words ${=}^5{{\mathrm{C}}_3}^3{\mathrm{C}}_{2}2!4!$