Can somebody me with these to questions how do you find the area of the circle

13)

Circumference (C) = 2π·r

11π = 2π·r

11/2 = r

Area (A) = π·r²

             =  π·(11/2)²  

            = 121π/4

           ≈ 94.985 in²

14)

diameter = 2r

          42 = 2r

           21 = r

Area (A) = π·r²

             =  π·(21)²  

            = 441π

           ≈ 1384.74 in²

$280/1384.74 in²

x = $0.20

about 20 cents per square inch

reduce the friction between its moving parts

step-by-step explanation:

in fact, by reducing the friction between the moving parts of the machine, it is possible to reduce the energy wasted due to this friction; therefore, more input energy is converted into useful work, and this will improve the efficiency of the machine.