Hope you can see my working that is attached below.
the side length of the smallest square plate on which a 20 cm chopstick can fit along a diagonal without an overhang is 14.14 cm long (to 2 d.p.) or if you want a more accurate answer you can leave the answer in surds for as 10[tex] \sqrt{2} [/tex] cm
Note: where i said OR in my working out I rationalized the surd to get it in the numerator.
