There are 362,880 different numbers that use the digits 1 to 9 exactly once (like 187,432,569).
Of these, what percentage are prime numbers?
(In reply to Puzzle Solution
by K Sengupta)
If instead, we were asked to evaluate percentage of prime numbers that use the digits 0 to 9 exactly once, then for each of the numbers the sum of the digits also would have been 45, so that each of the numbers having the said property must be composite, and consequently, the required percentage would have been 0.