Q. If any four numbers are selected and they are multiplied, then the probability that the last digit will 1,3,5 or 7, is
A) 4/625
B) 18/625
C) 16/625
D) None of these
Explanation
(c)
Total number of digits in any number at the unit place is 10.
$\therefore\ n(S) = 10$
To get the last digit in product is 1, 3, 5 or 7, it is necessary the last digit in each number must be 1, 3, 5 or 7.
$n(A) = 4$,
$\therefore\ P(A) = \frac{4}{10} = \frac{2}{5}$
Hence, required probability $= \left( \frac{2}{5} \right)^{4} = \frac{16}{625}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.