A number rounds off to 4000. The digit in the hundreds place is twice the digit in tens place. The sum of the digit is 12. The numbers uses only two different digits. Find the number.

Answer 1

4 x y z

x = 2 y but x is <5 so y = 0, 1, or 2

4 + 2y + y + z = 12
so
x + 3y + z = 8

if y = 0, then twice y is also 0 nope
if y = 1, then twice y = 2, nope 421 three digits
if y = 2 , then 4 4 2 z
then if z = 2, the sum is 12
how about 4422 ???

Answer 2

if the number is 3xxx with x>5, then the minimum sum is 3633=15 so, that will not work

If the number is 4xxx, then there must be 2 4's and 2 2's. That leaves only 4422 as a possibility.