PERMUTATIONS AND COMBINATIONS — MATHS STD 11 Science — Question
Gujarat BoardEnglish MediumSTD 11 ScienceMATHSPERMUTATIONS AND COMBINATIONS1 Mark
Question
How many 4-digit numbers are there with no digit repeated?
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Answer
Here total number of digits = 10 Number of digits used (no digit is repeated) = 4 Since 0 cannot be filled in the fourth place, so number of permutations for fourth place = 9 Now the remaining three places can be filled with 9 digits. $\therefore $ Number of permutations = $^9{P_3}$ $= \frac{{9!}}{{6!}} = \frac{{9 \times 8 \times 7 \times 6!}}{{6!}} = 504$ Hence total number of permutations $= 9 \times 504 = 4536$
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