According to your question, angles are in the ratio 1:2:3 right!

Let us consider the angle of the triangle are x, 2x , 3x respectively..

As sum of all angles in the triangle is 180 degree then x + 2x + 3x = 180

6x = 180 => x=30 degree

Angles are 30 , 60 , 90 degree

so , the smallest angle of all is 30 degree .. I hope you get your answer..Thank you...