Question

It is a four digit number the last digit is twice the first digit

Answer 1

Answer:There is no such number. Was this problem copied incorrectly from some other source?

For the digits a b c d

d = 2a

c = b

[cd] = [ab]

But then we have a, 2a, a, 2a but 2a<>a violating the c=b rule.

The only line of digits meeting this would be 0000. That’s not generally considered a four digit number. Just like 0003 is not generally considered a four digit number.