Question

Suppose repetitions are not permitted. How many three digit even numbers greater than 500 can be formed from the six digits 2, 3,5,6,7, 9. 

Answer 1

The first digit will be 5 or 6 or 7 or 9

Total = 4 ways

The second digit will be any remaining number.

Total = 5 ways

The third digit will be only even numbers 2 and 6

Total = 2 ways

By the law of Multiplication the required number of digits $= 4 \times 5 \times 2 = 40$