The leading digit can be only 1, 2 or 4  (only three possibilities)


The digit in the 2nd position can be any of 5-1 = 4 remaining digits;


The digit in the 3rd position can be any of 5-2 = 3 remaining digits;


The digit in the 4th position can be any of 5-3 = 2 remaining digits.


So the answer is:  3*4*3*2 = 72 four digits numbers are possible under the imposed restriction.

Pick the first digit as 1,2, or 4 to ensure that the number is less than 
5000.

That's 3 ways to pick the first digit.
That leaves 4 ways to pick the second digit.
That leaves 3 ways to pick the third digit.
That leaves 2 ways to pick the fourth digit.

Answer: There are (3)(4)(3)(2) = 72 four digit-numbers less than 5000 
which can be formed with digits 1, 2, 4, 6, 8 if no repetitions are 
allowed.

Here are all 72 (8 rows times 9 columns = 72 numbers)

1246 1248 1264 1268 1284 1286 1426 1428 1462 
1468 1482 1486 1624 1628 1642 1648 1682 1684 
1824 1826 1842 1846 1862 1864 2146 2148 2164 
2168 2184 2186 2416 2418 2461 2468 2481 2486 
2614 2618 2641 2648 2681 2684 2814 2816 2841 
2846 2861 2864 4126 4128 4162 4168 4182 4186 
4216 4218 4261 4268 4281 4286 4612 4618 4621 
4628 4681 4682 4812 4816 4821 4826 4861 4862

Edwin