Answer:
500
Step-by-step explanation:
So first off we know that there are 9000 (9k) natural 4-digit numbers -->
we solve using permutations so we can set the problem up like this
1 2 3 4
4 x 5 x 5 x 5 = 100 x 5 = 500
Reasoning:
So the reason we can do it like this is because -->
even numbers are: 0, 2, 4, 6, 8
ALL DIGITS MUST BE EVEN --> calculate using permutations simply makes it 5^4 but that's NOT our answer. Since the first digit can't be zero, we have -->
4, 5, 5, 5 respectively
Multiply this (by rule of permutations) to get, => 20 x 5 = 100
100 x 5 = 500
Thus, we have our answer of 500
Hope this helps!
