Answer
Addition of two three-digit numbers can be three digit number. For instance addition of $310$ and $420$ is $730$ which is a three digit number.
Work Step by Step
Here is an example in contrast to the statement that sum of two three-digit numbers is a four-digit number.
i.e. $310 + 420 = 730$
As shown above, the addition of $310$ and $420$ gives a three digit outcome which is $730$.
Hence, this is a clear contrast to the given statement
