Question

Find the product of all the odd natural numbers less than 5000.

Answer 1

The square of an odd number is an odd number:

10 < odd < 1,000
10 < odd^2 < 1,000
3.something < odd < 31.something (by taking the square root).

So, that odd number could be any odd number from 5 to 31, inclusive: 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, and 31.

14 numbers.