in cutting four equal circles,the largest,out of a square piece of cardboard of each side 10cm,how many square cm must necessarily be wasted

Each side of square board = 10 cm
So area of square board = ${\left(10\right)}^2 = 100 {\mathrm{cm}}^2$
When the largest four equal circles are cut from a square,
Then Diameter of each circle = $\frac{1}{4}\times \mathrm{each} \mathrm{side} \mathrm{of} \mathrm{square} = \frac{1}{4}\times 10 = 2.5 \mathrm{cm}$
Then radius of each circular part = $\frac{2.5}{2}$ = 1.25 cm
So area of each circle = ${\mathrm{\pi r}}^2 = \frac{22}{7}\times 1.25\times 1.25 = 4.910 {\mathrm{cm}}^2$
So area of four equal circles = $4\times 4.910 = 19.64 {\mathrm{cm}}^2$
Therefore area of part wasted = $100 {\mathrm{cm}}^2-19.64 {\mathrm{cm}}^2 = 80.36 {\mathrm{cm}}^2$