How many four letter word we can form from the word INEFFECTIVE
(i) 3 same of one kind & one different
(ii) 2 same of one kind, 2 same of other kind
(iii) 2 same, 2 distinct
(iv) all different
explain all step in this question with language
INEFFECTIVE1 = N, C, T, V2 = I, F3 = Eanswer= {all 4 letters different} + {2,1,1 letters} + {2,2 letters} + {3,1 letters}= 7P4 + 3C1 * 6C2 * 4!/2! + 3C2 * 4!/2!2! + 1C1 * 6C1 * 4!/3!= 840 + 3*15*12 + 3*6 + 1*6*4= 840 + 540 + 18 + 24= 1422