is 27, 36, 45 a pythagorean triad

Yep.....it's a multiple [of 9] of the basic triad 3 - 4 - 5

All multiples of the basic Pythagorean triads are themselves Pythagorean triads

Yes, it is, because:

45^2 =36^2 + 27^2. They are called "Pythagorean "triple".

\(\begin{array}{|rcll|} \hline \sqrt{27^2+ 36^2} = 45 \qquad \text{yes 27, 36, 45 a pythagorean triad} \\ \hline \end{array} \)