Answer:22.4 cm
Explanation:
First draw the rectangle and divide it into two triangles.
Take one triangle out and with the length and breath solve for the hypotenuse using Pythagoras theorem
.: H^2 = 10^2 + 20^2
H^2 = 500
Find the square root of both sides of the equation
H = 22.4 cm = the length of the diagonal