Question

If any four numbers are selected and they are multiplied, then the probability that the last digit will be

1, 3, 5 or 7 is

• A. 4/625
• B. 18/625
• C. 16/625
• D. None of these

Answer 1

Answer: (C)

16/625

Answer 2

Total number of digits in any number at the unit place is 10.

\ 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(1) = 4, \ P(1) = $\frac { 4 } { 10 } = \frac { 2 } { 5 }$

\ Required probability = $\left( \frac { 2 } { 5 } \right) ^ { 4 } = \frac { 16 } { 625 }$