What is the diagonal of 10 by 20?

To find the diagonal of a rectangle measuring 10 units by 20 units, you can use the Pythagorean theorem. The diagonal ( d ) is given by the formula ( d = \sqrt{(length^2 + width^2)} ). Plugging in the values, we have ( d = \sqrt{(10^2 + 20^2)} = \sqrt{(100 + 400)} = \sqrt{500} ), which simplifies to ( d = 10\sqrt{5} ) or approximately 22.36 units.