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NCERT Class XI Mathematics - Permutations and Combinations - Solutions

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Question : 31 of 41
Marks: +1, -0
How many words, with or without meaning, each of 2 vowels and 3 consonants can be formed from the letters of the word DAUGHTER?
Solution:  
Total no. of letters in the word DAUGHTER = 8,
No. of vowels in the word (A, U, E) = 3
No. of consonants in the word (D, G, H, T, R) = 5
So, words can be formed with 2 vowels & 3 consonants in (32)×(53)\binom{3}{2} \times \binom{5}{3} ways.
∴ Required no. of words = 5P5×(32)×(53){}^{5}P_{5} \times \binom{3}{2} \times \binom{5}{3}
= 5!0!×3!2! 1!×5!3! 2!\frac{5!}{0!} \times \frac{3!}{2!\,1!} \times \frac{5!}{3!\,2!} = 5×4×3×2×5×4×3×22×2\frac{5 \times 4 \times 3 \times 2 \times 5 \times 4 \times 3 \times 2}{2 \times 2} = 3600
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