The angles of a triangle are in the ratio 3 : 4 : 5. The triangle is :

acute angled triangle

Let the angles of triangle be 3a, 4a and 5a respectively,

⇒ 3a + 4a + 5a = \({180}^\circ\)

⇒ 12a = \({180}^\circ\)

⇒ a = \({15}^\circ\)

The angles of triangle are,

⇒ 3a = \({45}^\circ\) , 4a = \({60}^\circ\) , 5a = \({75}^\circ\) ,

As, all angles are less than \({90}^\circ\)

Therefore, it is an acute angled triangle.