At 3.40, the hour hand and the minute hand of a clock form an angle of:

Angle traced by hour hand in 12 hrs. = 360º.

Angle traced by it in  11/3 hrs=   $\frac{360}{12}*\frac{11}{3}°$= $110°$

Angle traced by minute hand in 60 min. = 360º.

Angle traced by it in 40 min. =(360/60*40) $°$=240 $°$

  Required angle (240 - 110)º = 130º.