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)`

Answer 1

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.