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Question
A car has two wipers that do not overlap. Each wiper has a blade of length 21 cm sweeping through an angle of 120°. Find the total area cleaned at each sweep of the blades. `("Take" π =22/7)`
Solution
Radius = r = 21 cm
sweeping angle = 120°
Total area cleaned by two wipers `= 2 xx "area cleaned by one wiper"`
Total area cleaned by two wipers `= 2 xx "area of sector with" 120^@`
`= 2 xx theta /360 xx pi"r"^2`
On substituting the values `= 2 xx 120/360 xx 22/7 xx (21)^2`
`= 2 xx 120/360 xx 22/7 xx 441`
`= (2 xx 22 xx 147)/7`
`= 6468/7 = 924`
Therefore, the area cleaned by both wipers is 924 cm2.
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