A) 69760
B) 2912
C) 98748
D) 987147
Correct Answer: A
Solution :
Idea Here, number of permutation of n dissimilar things taken r at a time \[{{=}^{n}}{{p}_{r}}=\frac{n!}{(n-r)!}\]repetition is not allowed total ways \[={{n}^{r}}\]Number of 5 letters word if at least one letter is repeated is equal to = Total possible 5 letters word Number of 5 letters word when repetition is not allowed \[={{10}^{5}}-10\times 9\times 8\times 7\times 6\] \[={{10}^{5}}-30240\] \[=69760\] TEST Edge Fundamental theorem of permutation and their application based questions are asked. To solve such type of question, students are advised to understand the concept of fundamental theorem.
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