What property is used with (1.6×2) ×5 and ( 27 × 2.5 ) × 4

The associative property is used for both of these. (1.6*2)*5 can also be 1.6*(2*5) and it would still give you the same exact answer. Same goes for (27*2.5)*4. I hope that helps!

“exterior angles of triangles. an exterior (or external) angle is the angle between one side of a triangle and the extension of an adjacent side. try this drag the orange dots on any vertex to reshape the triangle.” look to get to the answer i explained what it means and other things i hope it you .