Here's why:
sqrt(49) = sqrt(7^2) = 7
We can write 7 as a ratio or fraction of two integers 7 = 7/1
This shows that 7 is rational, so that makes sqrt(49) rational as well.
An irrational number is one where we cannot write it as a fraction of two integers. An example of an irrational number would be pi. Another irrational number is sqrt(2).
Note: the denominator can never be zero.
