Question

If four whole numbers taken at random are multiplied together, then the probability that the last digit in the product is 1, 3, 7 or 9 is

• A. $\frac{16}{625}$
• B. $\frac{32}{625}$
• C. $\frac{64}{625}$
• D. $\frac{256}{675}$

Answer 1

The correct option is A $\frac{16}{625}$

All four numbers should end with either digit $1$ or $3$ or $7$ or $9$ to get last digit of their product as $1,3,7,9$
The required probability of choosing such four numbers $=4\ast 4\ast 4\ast 4\ast /(10\ast 10\ast 10\ast 10)=16/625$