The angles of a triangle are in the ratio 3 : 4 : 5, then the smallest angle in degree and the greatest angle in radians is 

$\angle A=3x°,\angle B=4x°,\angle C=5x°$

$A+B+C=180°$

$3x+4x+5x=180°$

$12x=180°$

$x=15°$

$\therefore$ Smallest angle = 3x = 3(15°) = 45°

Greatest angle $=5x=5\left(15\right)=75°$

                        $=75\times \frac{\pi }{180}=\frac{5\pi }{12}$ radians