Answer:
20inches
Explanation:
The length of the diagonal is gotten by using the pythagoras theorem as shown;
l^2 = h^2 + w^2
l is the length of diagonal
h is the height
w is the width
l^2 - 16^2 + 12^2
l^2 = 256 + 144
l^2 = 400
l = √400
l = 20in
Hence the length of a diagonal of this picture frame in inches is 20inches