The minute hand completes a full rotation of 360° in 60 minutes.
Speed of minute hand =60 min360°=6° per minute
The hour hand completes a full rotation of 360° in 12 hours (720 minutes).
Speed of hour hand =720 min360°=0.5° per minute
Time taken for the minute hand to move 240°:
Time=6° per minute240°
Time=40 minutes
In 40 minutes, the hour hand moves:
Movement=0.5° per minute×40 minutes
Movement=20°
Therefore, the hour hand moves 20°.