The number of five digit numbers that contain 7 exactly once is
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a
(41)93
b
(37)93
c
(7)94
d
(41)94
answer is A.
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Detailed Solution
When 7 is right in the beginning, the number of numbers = 94 and when 7 is not in the beginning, the number of numbers is (C1 4) (8) (93)∴ Required number of numbers =94+ 4C1(8)93=(41)93