A) \[\frac{10\ !}{6}\]
B) \[3\ !\ 7\ !\]
C) \[^{10}{{P}_{3}}\ .\ 7\ !\]
D) None of these
Correct Answer: A
Solution :
For A, B, C to speak in order of alphabets, 3 places out of 10 may be chosen first in \[1\ .{{\ }^{3}}{{C}_{2}}=3\]ways. The remaining 7 persons can speak in \[7\ !\] ways. Hence, the number of ways in which all the 10 person can speak is \[^{10}{{C}_{3}}\ .\ 7\ !\ =\frac{10\ !}{3\ !}.=\frac{10\ !}{6}.\]
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