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NDA 2024

Exam: NDA
Year: 2024
Subject: Mathematics
Chapter: Permutation and Combination

NDA 2024 · Mathematics · Permutation and Combination

How many 4-digit numbers are there having all digits as odd?

How many 4-digit numbers are there having all digits as odd?

Options

A $625$
B $400$
C $196$
D $120$

Correct answer

A. $625$

Step-by-step solution

Odd digits can be

1,3,5,7,95 \times 5 \times 5 \times 5

\because \quad

All five odd digits can be filled at 4 places. Hence total required 4-digits numbers are

5 \times 5 \times 5 \times 5=625

.

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