Four whole number taken at random are multiplied together.

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Four whole number taken at random are multiplied together. The chance that the last digit in the product is 1, 3, 7, or 9 is ?

1. 16/625
2. 1/210
3. 8/125
4. 4/25

Correct Option: A

If the product of the four numbers ends in one of the digits 1, 3, 7 or 9, each number should have the last digit as one of these 4 digits.
∴ The number of favourable cases = 4⁴
Total number of all possible cases = 10⁴
Hence, the required probability =4⁴/10⁴
= 2⁴/5⁴ = 16/625