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Permutations Practice Test 2
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© examsnet.com
Question : 25
Total: 30
The number of 5-digit telephone numbers having at least one of their digits repeated is:
90000
10000
30240
69760
Validate
Solution:
A telephone number can be started with zero. Therefore the number of numbers with atleast onedigit repeated
=
10
5
−
10
P
5
=
10
5
–
(
10
.
9
.
8
.
7
.
6
)
= 69760
© examsnet.com
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