Correct Answer - A
The divisibility of the product of four numbers depends upon the value of the last digit of each number. The last digit of a number can be any one of the ten digits 0,1,2,..,9. So, the total number of ways of selecting last digits of four numbers is
10
×
10
×
100
×
10
=
10
4
10
. If the product of the 4 numbers is not divisible by 5 or 10, then the number of choices for the last digit of each number is 8 (excluding 0 or 5).
So, favourable number of ways
=
8
4
=
.
Therefore, the probability that the product is not divisible by 5 or 10 is
(
8
/
10
)
4
(
Hence, required probability
=
1
−
(
8
10
)
4
=
369
625
=
