Question 713120
The sides of the rectangle must measure 3cm and 4cm, because those are the only consecutive positive integers that multiply to give 12.
A right triangle with legs measuring 3 and 4 cm has a hypotenuse measuring 5 cm.
You could calculate it using Pythagoras, but (3,4,5) is the most popular of the Pythagorean triples
(and the only one I remember).
So the diagonal measures 5 cm.
(Someone got too enthusiastic with the squares and added 2 as exponent to all the answers, but le.gths are measured in plain cm; square cm are for measuring surface area).