how do i find the radius of the largest circle that can be cut from a square piece of paper with a diagonal of 20cm?

Answer 1

Diameter = Length of a side. = X.
X^2 + X^2 = (Diag.)^2,
2X^2 = (Diag.)^2 = (20)^2,
2X^2 = 400,
X^2 = 200,
X = sqrt(200) = 14.14cm = Diameter.

r = 14.14 / 2 = 7.07cm.