Respuesta :

The measures of the interior angles of a triangle have sum 180°.

Since the measures of the angles are in the ratio 1:4:5, we can call them 1x, 4x, and 5x, for some positive integer, x.

So, x + 4x + 5x = 180

10x = 180

x = 18 4x = 72, 5x = 90