Question
Download Solution PDFHow many four-digit natural numbers are there such that all of the digits are odd ?
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFCalculation:
Odd digits - 1, 3, 5, 7, 9
A four-digit number with all digits odd has 5 choices in the first position, and since digits can be repeated, there are 5 choices for the second, third, and fourth positions also.
So, the number of four-digit natural numbers such that all of the digits are odd = 5 × 5 × 5 × 5 = 625
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