A. 63
B. 126
C. 45
D. 90
Required number of ways = (7C5 x 3C2)
As nCr = nC(n-r) we can write as
= (7C2 x 3C1)
= 63
How many 4-letter words with or without meaning, can be formed out of the letters of the word, LOGARITHMS, if repetition of letters is not allowed?
In how many different ways can the letters of the word MATHEMATICS be arranged so that the vowels always come together?
In how many different ways can the letters of the word OPTICAL be arranged so that the vowels always come together?