Explicație pas cu pas:
diameter of the bar = side of the square
=> d = 12 cm
diameter of the hole = 6 cm
=> radius of the hole = 3 cm
area of the square:
=> A = 12² = 144 cm²
area of the final nut:
A₁ = (6² - 3²)π = 25π cm²
lost area:
=> A₂ = A - A₁ = 144 - 25π cm²
the percentage of the bar volume that is lost through processing:
p = V₂/V = (12×A₂)/(12A) = A₂/A = (144 - 25π)/144 ≈ 0,45
p ≈ 45%