The hour hand of a 24 hour clock moves from 13:15 p.m. to 17:45 p.m.
If the length of the hour hand is 3.5 cm, find correct to three significant figures, the area swept by the hour hand.
[Take π = ]
Show Solution
Area of a sector
Area of a sector = x area of the circle
Area of a sector = x π x radius x radius
There are 12 hourly division for the clock.
Angle per hour = = 30°
Angle of the sector of the hour hand swept = hours x 30°
The hours from 13:15 to 17:45 is 4.5 hours
Angle of the sector of the hour hand swept = 4.5 x 30° = 135°
The length of the hour hand is the radius of the circular clock.
Radius = 3.5
π =
Area swept by the hour hand = x x 3.5 cm x 3.5 cm
Area swept by the hour hand = 14.4375 cm2
Area swept by the hour hand = 14.4 cm2(three significant figures)