1.

How many different words can be formed from the letters of the word ‘GANESHPURI’? In how many of these words:(i) the letter G always occupies the first place?(ii) the letter P and I respectively occupy the first and last place?(iii) Are the vowels always together?(iv) the vowels always occupy even places?

Answer»

Given as

The word ‘GANESHPURI’

Here 10 letters in the word ‘GANESHPURI’. Total number of words formed is 10P10 = 10!

(i) the letter G always occupies the first place?

If we fix the first position with letter G, now remaining number of letters is 9.

Number of arrangements of 9 things, taken all at a time is 9P9 = 9! Ways.

Thus, a possible number of words using letters of ‘GANESHPURI’ starting with ‘G’ is 9!

(ii) the letter P and I respectively occupy the first and last place?

If we fix the first position with letter P and I in the end, now remaining number of letters is 8.

Number of arrangements of 8 things, taken all at a time is 8P8 = 8! Ways.

Thus, a possible number of words using letters of ‘GANESHPURI’ starting with ‘P’ and ending with ‘I’ is 8!

(iii) Are the vowels always together?

Here 4 vowels and 6 consonants in the word ‘GANESHPURI’.

Considering 4 (A,E,I,U) vowels as one letter, now total number of letters is 7 (A,E,I,U, G, N, S, H , P, R)

Number of arrangements of 7 things, taken all at a time is 7P7 = 7! Ways.

(A, E, I, U) can be put together in 4! Ways.

Thus, total number of arrangements in which vowels come together is 7! × 4!

(iv) the vowels always occupy even places?

The number of vowels in the word ‘GANESHPURI’ = 4(A, E, I, U)

The number of consonants = 6(G, N, S, H, R, I)

The even positions are 2, 4, 6, 8 or 10

Then, we have to arrange 10 letters in a row such that vowels occupy even places. Here 5 even places (2, 4, 6, 8 or 10). 4 vowels can be arranged in these 5 even places in 5P4 ways.

The remaining 5 odd places (1, 3, 5, 7, 9) are to be occupied by the 6 consonants in 6P5 ways.

Therefore, by using the formula,

P (n, r) = n!/(n – r)!

P (5, 4) × P (6, 5) = 5!/(5 – 4)! × 6!/(6 – 5)!

= 5! × 6!

Thus, number of arrangements therefore that the vowels occupy only even positions is 5! × 6!



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