How many circular plates of diameter d be taken out of a square plate of side 2d with minimum loss of material?

Area of square plate = (Side)²
= (2d)²
= 4d²
Area of circular plate = π (d/2)²
= πd²/4
∵ Number of square plates
= [(4d²)/4] / [(πd²)/4]
= (4 x 4)/π
≈ 5
Since, nearest integer value is 5.