Rounded to one decimal place means to round to the nearest tenth (i.e. to the nearest 0.1)
4.25 (rounded to the nearest tenth) = <u><em>4.3</em></u>
Exterior angles always add up to 360 degrees so for 30-gon each exterior angles is 12 degrees (360/30)
To get the interior angles you subtract 180 from 12 to get 168 degrees
35.39, 35.38, 35.37, 35.36 are some numbers that round to 35.4 when rounded to the nearest tenth
