the formula for area of a circle = PI x r^2
since we know area, we can put that in the formula and solve for r ( which is the radius) diameter is radius x 2
826 = 3.14 x r^2
divide both sides by 3.14:
r^2 = 826 / 3.14
r^2 = 263.06
r = square root (263.06)
r = 16.22 cm
diameter = 16.22 * 2 = 32.44 cm